"Mainstream" implies large. The issue is individual. I am very comfortable with the members of my local Baptist Church, but the convention has a history of going off on rediculous stuff. This is generally an ego thing, where ego gets in the way of what should happen. The "I know what is better for everyone else" syndrone.
I'm 'non-denominational' now though. The greatest non-demominational 'minister' I've ever met though is a guy in NM that preaches in two churches miles apart every Sunday - he showed up with a pickup truck full of lumber. and without a word, started rebuilding my brothers home that was damaged by fire. He has fixed peoples cars, cared for the sick and infirm... and I am certain about one thing - he will be among the greatest in heaven.