It doesn't surprise me that the most significant contempt and hostility to Christianity comes from the left. It is liberals, after all, who look at the government as the primary source for good, and for social change, in society. And, religion is their most significant competition to government in that regard.
A lot of this attitude comes from an emphasis on good works over salvation in the minds of liberals. I know from experience that many liberals don't even want to hear about sin, and repentance, and forgiveness, and salvation. The only thing they want to hear is about love, and caring for neighbors. It's no wonder that liberals frequently decide that they don't need the church at all, because government is taking over that role in their lives. So, even if they stay in the church, the church becomes just another politically liberal non-profit with a cross on the wall.
