I have been hanging around at church for 55 years. I was born a preacher's kid, and I have visited far in excess of 1000 churches across the years. So I think I have a little perspective. I am able to say with some accuracy: theology is no predictor of meanness (or kindness) in a congregation. The spirit of meanness seems to be an equal opportunity visitor - afflicting some of the most conservative and some of the most liberal congregations in America. It comes out in different ways - sometimes in rude interactions, and just as often in passive ways. Christian congregations can be some of the meanest places on earth - and some of the most grace-filled. And often, we are talking about the same church!
My dad served a church in the 1950s where the people got into a fight at a church meeting and threw chairs at one another in the fellowship hall. A kid had to go call the police. I heard this story growing up, and assumed that this was just a quirk related to a rough and tumble church of poor white folks in Fort Worth. But, the years have revealed that with education and a little money, the only difference is that we stop throwing chairs. Nothing else changes.