the definition of a militant agnostic:

" I don't know and neither do you"

Education its the medicine...

I think what you observed happened for three reasons.

First, most atheists in the US are from a christian background and family, and from what I understand christianity in the US is agressive, ubiquitous, punitive, and ironically unforgiving. I think former US christianity believers go through a lot more arguing and defending, and have faced more loss than I, who never experienced any serious religion, have. Im not sure how I'd behave if I meet someone who supports a system that caused me personal loss. How would you behave if you saw someone support the kkk or nazis? How would a black person or a jewish person behave?

Second, Christopher Hitchen and Richard Dawkins. Over the last ten years, in response to the rise of militant religious in both islam and christianity, we got two very outspoken, educated, high profile, and beyond charismatic atheist debaters that inspired a whole generation of atheists to take the offensive. There's a reason these two of the four Horsemen are the most popular. They were aggressive attackers of religious people, and did it with style. %hey were heroes who defeated an enemy. The other two, daniel Dennett and sam harris, were much more nice and pleasant, comparatively. So we have Hitchens and Dawkins to thank for a generation of aggresive atheists.

Third, atheism attracts certain kinds of people. People who like to go against the status quo (contrarians), people who want to be different from the rest (indivudualists), people who want to be persecuted, people who want to fight for a cause, people who prefer to be underdogs in a fight...people who want a fight, any reason to be mean and nasty to others.
Sadly these sort seem to make up a lot of vocal atheists right now.

What I would give to have the current rational folk reputation be "kind, helpful, trustworthy, just all around good decent people". Building the reputation of our group is and should be a serious thing.

Look at the Mormons, as persecuted as they are, as crazy their religion is, they have cultivated a reputation of being nice, kind, people.

I'd atleast like that as a starting reputation in our society for all rational folk!

It could be that they are bitter and belittling from being belittled, bullied, dismissed, and generally abused by the religious. Or that the religious keep trying to pass laws based on their beliefs. For many being tolerant and compassionate about a religious belief feels as icky/stupid as being tolerant and compassionate of a racist.

Agnostics need to work more on building an support network instead of hyper-focusing on challenging Christians. Covert people to Humanism by making Humanism fun.

I think it is about having places and events where communities come together. Something has to take the place of the Church in driving these things, and that means having people to organise it, a place where it can happen, and some form of central activity.

Live and let live. Block and ignore.

Honestly, I don't think that a totally inclusive community is feasible. Due to our nature, we inherently want to be right and a lot of people are afraid of being wrong. Now this isn't to say that there cannot be agreement, as we're all part of a spectrum, but as you get to the farther edges, you tend to be less willing and even less able to hear other POV.
Personally I think that the best that we can hope for a consensus on the big things, which means that we'll all have to hold our noses and breathe together. In terms of religion, I think that it means accepting that some people believe in divinity, for those that are religious it will mean accepting that people have the right to disagree and dispute their beliefs - we're a long way away from those times. That said, there is always opportunity for understanding.

The problem is were outnumbered, there has never been atheist member of Congress.

although there have been some openly gay members of Congress.

Religion in the United States (2016) Protestantism (48.9%) Roman Catholicism (23.0%) Mormonism (1.8%) No religion (18.2%) Judaism (2.1%) Muslim (0.8%) ...
Religion in the United States, Gallup, 18+ (2016) Protestantism (48.9%) Roman Catholicism (23.0%) Mormonism (1.8%) No religion (18.2%) Judaism (2.1%) Muslim (0.8%)
when I see how people live their lives, as an atheist I don't feel so lonely.

Atheists are just another form of pendantic, dogmatic true believers, and if you dare to disagree with their absolute certainty there is no god or afterlife in any form or definition you are WRONG.
Agnostics are much more open-minded.
I for one don't think there's a god if you mean a "supreme being," but I realize our civilization is very young and likely to collapse anyway, because of that very facet of human nature which leads to such absolutist thinking. Maybe if the human species evolves, and learns to respect other points of view, it will survive long enough to actually learn more about the universe, and come up with more nuanced and sophisticated ideas about the nature of life in all its dimensions.
In the meantime we're stuck with this.

The lefter the atheist the more looney. "Conservative" atheists are much more accepting.
That is so crazy to me being a life-long classical liberal.

@lifelonglearner Check out [aeu.org] and other Ethical Unions and Societies. Their mission and vision is as follows:

The American Ethical Union creates, nurtures, and inspires ethical humanist communities to foster a world that is democratic, compassionate, just, and sustainable.

Ethical Humanism/Ethical Culture is a humanist Movement focusing on human goodness and building ethical relationships with each other and the Earth. As a non-theistic organization we do not concern ourselves with the existence or non-existence of a deity but instead embrace the diversity of our membership.

We recognize the unique worth and dignity of all people regardless of their race, ethnicity, sexual orientation, sexual identity, economic status, level of ability, or religious beliefs.

We advocate for reason, compassion, and rational thinking so we can progress as individuals, communities, and a world.

We act to elicit the best in others and thereby in ourselves, celebrating with and supporting each other through life.

We realize the full capacity of our human spirit when we stimulate our thinking with new insights and inspirations.

We are recognized as a religious movement because for us the ethical quest has the depth of a religious commitment, and because we recognize the value of a community of support, celebration, and action.

We train future humanist leaders to promote responsible and ethical living.

I'm not a member but I think is a great idea for community building!

I believe based on my personal experience that certain qualities make a person able to connect better with whatever community they are a part of, however difficult that community's traits are. These qualities are things like being open-minded and knowing how to respectfully set boundaries. It's my belief that if you possess those traits you will be more comfortable along any group of people but you will also tend to draw others to you who share your qualities.

I tend to agree with you, to an extant. Most non-believers like myself that I know tend to belittle believers. Now, I used to do this myself, and at times I certainly still want to. "What don't they get?!!!!" and so on. But I do know this; it took years for me to absolve myself of things that were ingrained in me during childhood, all from a pair of alcoholic parents and their extended families, and all with negative re-inforcement. These people tried to convince me I was considerably less a human/man than I am for their own benefit (just not going into details here). I had a vested interest in proving them wrong, and though its taken years, I have. But I have to imagine how hard it would have been to overpower their lies and falsehoods if it had been positively re-inforced instead, like most of the Christians I know most likely were. Many of the believers I know simply want to continue to believe, even those who see impossibilities in the premise, simply because it feels good to them. (Frankly, they seem to vote the same way.) They see no plus side to venturing into an area not represented in their childhood, and so don't. The logic is meaningless to them, and if they did broach the topic, they would have to admit to themselves they were lied to/fooled/brainwashed/whatever by their parents, and they simply won't go there. And it won't do us any good to continue to belittle and insult those who, for whatever reason, simply can't make that leap. It will take many more generations for society to see past the false premises of religion, and the only way to show them some truth later is to have our hand out to them. I know I sound like a bleedin' lefty here, (and I am one) but really, nothing else will ever work. We need to keep our frustrations to ourselves ( in places like this, so we can air them out) and remain as civil as is possible elsewhere.I love cutting down a fundamentalist as much as the next Agnostic, but in public, at least for the last few years, I try to remain tolerant without leading them to believe I'm one of them. Eventually they see I'm agnostic/humanist/whatever and, son of a bitch, I'm not evil; Who-da thunk it.

i've never heard of such a thing as atheist communities, an american construct? i do know that some atheists never manage to break out of the anger stage.

All the de-platforming that is happening at colleges, all the banning on twitt, YT,... is by people who call themselves liberals and progressives.
No conservatives are protesting "liberal" speakers.
Just as the OP opined: all those most militant and insulting call themselves LEFTISTS.

Looking at your profile, why not try to find a Buddhist community? Lots of nice atheists in those.