I am so sorry to hear about your problems. People will give you a wide berth if you are unremittingly negative, and at least you realise this. What you really need to do is have some Cognitive Behaviour Therapy to get you in a more positive frame of mind. Can’t imagine what it must feel like to be in your shoes as I am one of life’s optimists.

No, it's not unethical to want to be in a group, it's part of human nature. But...if you are a toxic person and are aware of that you kind of have a responsibility to yourself and others to look at that at least.

I think that what you have identified is that you are not the best company for most people, this probably means you're not really enjoying your own company?

Can you accept yourself as you are?

I found an article online that I thought might help but my malware didn't like the site so I copied and pasted it (I don't think the doing nice things for people ones are as important as being in control of yourself...but whatever works for you) :

I was driving to town the other day, when, at some point on the highway, I found myself near a huge truck. I don’t know if you know the type: ugly, noisy and… toxic! The exhaustion pipe was left oriented, and since the truck was rolling on my right, even if my windows were closed, I was inhaling huge amounts of gas. Toxic gas.
After a few hundreds meters I went ahead of it and looked to the rear mirror: the driver didn’t seem to have any problem with all that toxic gas he was literally exhaling on the highway. He looked calm and somehow on top of the situation. I could see he had no idea he was a really toxic person to other people.
The day went on as usual but on my way home, around the same place I met the truck, something hit me: we can all be toxic persons to other people, only we don’t realize it. We’re going on and on, relaxed and somehow on top of the situation without even noticing how infectious we can be at times, just like the driver of the morning truck. We can all spread gas on other people cars, so to speak, and the worst thing is we don’t even realize how toxic we are.
Once home, I started to think about what makes us toxic persons. Even more, I tried to identify some simple ways to avoid becoming such a person. What follows is only a short list of what I found. Generally speaking, I was searching for things which can lower your toxic “gas emissions”, making it easier to become an “ecological” citizen. The list is not even near to be complete, so feel free to add your own tips in the comments.
1. Say Thank You
Sometimes you simply forgot to say “thank you’, sometimes you’re in a hurry, or sometimes you just don’t want to say it out loud. But fact is, every time you’re not saying “thank you” you leave room for a toxic thought or approach. The simple act of saying “thank you” closes an interaction in a completely healthy way, no room left for any potential harmful follow up.
2. Say Only What You Mean
It’s not only about plain lying, although it encompasses this too. It’s about keeping what you’re saying in sync with your mind, goals and attitude. The moment you’re starting saying things you don’t really mean, your communication process becomes heavily ineffective, hence you’re going to emit huge amounts of toxic gas, just like that ugly, noisy truck.
3. Clearly State What You Want
A lot of toxicity exhales from misunderstanding. Small confusions, false impressions or misinterpretations are like glitches in a car engine. Every time you get such a glitch, it’s like having water in your gasoline: the conversation engine will start to cough and before you know it, you’ll get an increased level of toxicity. Just say what you want.
4. Say Something Nice To An Unknown Person
Like it or not, we do live in an emotionally polluted world. Doesn’t matter if this emotional pollution comes, most of the time, from people who don’t even realize they’re toxic, like the driver of that truck. What really counts in this dusty environment is to try lowering this pollution index as much as we can. And saying something nice to a completely unknown person will have exactly this effect: it will act like an air freshener, making the smog disappear at least for a few moments.
5. Don’t Gossip
Talking behind other people’s back is like putting your exhaustion pipe to somebody else door, while pretending you’re looking in a different direction. Even if you’re not talking directly to those people, you’re directing your toxic emissions to their houses. Sooner or later they’ll realize something is wrong and they’ll also identify the source.
6. No Regrets
Even if you don’t realize, when you regret stuff for yourself you’re affecting the reality of others too. Even if your regrets have nothing to do, directly, with their reality. The mere act of keeping strings attached to the past will make you be that driver who’s going ten miles per hour on a speed lane. This apparently small inconvenient of not letting others go faster will soon become toxic for them.
7. Pay Attention To People Around You
For starters, just look around and realize there are other people around you, that would be enough. A lot of toxicity arise from ignorance. If the driver of that huge truck would have look at me he could have seen that I was a little bit upset because of all this gas. But he just assumed that everything was ok, without checking. Most of the time we do the same.
8. Help Somebody Around
If “saying something nice to an unknown person” will act like an air freshener, helping somebody around will be equivalent to a full repair of a damaged exhaustion pipe. Helping other people will lower not only their existent toxicity but it will also drastically reduce the odds of an uncontrolled increase. If you help somebody out, you will in fact create a fresher environment for yourself.
9. Give Your Time To What’s Important
If you’re drifting away from task to task, without focusing on what’s really important all you’re going to do is to create an awfully crowded traffic. It’s like driving in circles on the same roads again and again, without doing anything from what you intended to. The only problem with that is that you’re becoming a problem too. If you can’t focus, move away from the road and let others reach their goals.
10. Let Go Of The Unneeded
Clutter is bad. Period. Loading yourself with tons of unneeded gadgets or beliefs will make you move slower and slower. Be elastic, be slim. Adjust instantly to new environments. If you can’t do that, you’ll be like a 4×4 car carrying away a huge truck. Not only your mileage will sky rocket, but your overall performance will go down. You will become toxic by immobility.
11. Avoid Procrastination
How many times you went in circles in a public parking waiting for a free spot? Well, if you procrastinate, you’re one of the guys keeping a parking spot for ever. And that’s pretty frustrating. Procrastination is not only an individual choice, it will affect your interaction with other people too. If you’re not doing your job, you’re infecting others with your behavior.
12 Don’t Talk Bad About Yourself
It’s contagious. Other people can borrow this attitude pretty easily and that would create some sort of an epidemic. Not to mention the fact that talking bad about yourself it’s like scratching your own car, because you think it “deserves” that. Yeah, if we’re talking about a car it’s kinda funny, right? How can one scratch his own car? But at the same time we keep talking bad about ourselves. Try to visualize yourself walking around with a lot of scars for your own punches…
13. Don’t Enter A Fight**
Fighting – as in verbal fighting – it’s such a waste of time. Have you ever noticed those drivers fighting when someone blunders in traffic? They spend minutes and minutes blocking the road just to tell how smarter and skilled they are, and how stupid the other guy is. Meanwhile, the road is blocked, everybody is delayed and the toxic gas from the immobilized cars is slowly replacing the oxygen.

Dragos Roua

P.S. if you're still reading...learning a new skill, doing a class might be good too, that way you're still interacting with people, but there are set perimeters to the contact, plus you get a new skill too.

First, its your choice to own the labels put upon you by society, and define yourself as such.
Second, ethics be damned, you have as much right to exist and enjoy your life as other people. It might behoove you to create your own group designated as deliberately welcoming negative people and other social outcasts to salve your conscience.
Third, sure its rational to discriminate against anything or anyone that makes you unhappy. But is it healthy to insulate yourself against people's differences? You can learn something from everyone if you consider the world your classroom and people your teachers.

That's a really tough question

I believe the answer to your question is "yes" as long as you are willing to accept the consequences of any inappropriate behaviour.