Fear?
I fit into this category. I was raised Catholic, but have drifted away from any social religion. To me religion is personal.
Because of this I have never been flamed. Arguing with others about religion seems useless. The purpose of religion should be to lead a more spiritual life, not to convince others to, IMHO.
About the only thing I like to do to others who claim to KNOW the truth about God is to remind them that they are but one of billions of organisms on one planet out of trillions in a vast universe, and that they really don't know anything at all. A real, modern-day flat earth society...
FReegards...