Religion is the most effective long con ever perpetrated.
[rawstory.com]

When the religious person thinks they're smarter than me and I'm going to burn in hell!

For me, the most I'll tolerate is "Eh, I never thought about it. I just always called myself Catholic because I came from a Catholic family."

As long as their inactive it's normally fine.

I have pondered this. many times. For me it has to do with my children, I do not mind dating a religious person as long as they respect my being an agnostic atheist. The deal breaker for me would be if they differed in how to raise my kids because of their belief in their religion.

Depend on the religion. In general, it doesn't take much. In the case of LDS, I have run across too many issues with even the ex-LDS. The brain washing many of them went through as kids is nothing short of abuse and has serious permanent effects.

An online profile that specifically states a belief in a savior or devotion to God is a definite crossed line for me.

"You shouldn't hang out with <person> because <theological reason>," basically if it gets to the point where religion is the basis for judgemental behavior then we're done. Alternatively, if your adherence to a belief system makes you someone I wouldn't introduce to my casual friends (or acquaintances) then I wouldn't try dating you in the first place.

Even the term spiritual is a deal breaker.

Realistically if they're even a little bit religious it's going to lead to problems eventually, unless you're willing to go through life smiling and nodding every time they talk about it.... every religious person I know thinks they're 100% right and everyone that believes differently is wrong, it's a recipe for disaster.

Fundamentalist.

If they have an online profile and feel the need to mention god/religion in their blurb or interests. I mean, there's check box for your religion.

I wouldn't be able to live with someone who was that intellectually dishonest.

It's actually a deal breaker for me right off the bat now. Everytime I've tried to date someone who was religious/spiritual, they eventually tried to bring me to their side and it gets ugly. Or they may accept me but once I met the religious family it all goes to crap because they try to convert me and I'm not great at holding my tongue

I just don't find it attractive to date someone who is at all religious. I just know I'll eventually pick an argument about it and I'm just not interested in having that in my relationships.

The minute they go beyond conversation to pushing opinions or indicating you are wrong for what you believe.

only if its harmful.. if it keeps them from advancing

To the point of where they try and control you and treat you differently.

Red flag is raised when they try to change you

The only problem I would have dating a religious person is if they were trying to change me and didn't have the same respect for my beliefs as I would for theirs.