Christianity, like every other idea, is haunted by what I would call “the momentum of stupid”. It is a combination of many things, resulting in the ignorant and arrogant portraying the idea in the worst possible light, while advocating for it. Usually without being asked to.
There is no end to the damage that the momentum of stupid can accomplish to an idea, including bloody wars. Even a single such advocate can wreak destruction that will take dozens or hundreds of intelligent advocates decades or centuries to repair.
The greatest example of this afflicting Christianity is probably the life and times of a man named Hong Xiuquan. With just the slightest introduction to Christianity, he decided that he was Jesus’ younger brother, and started a civil war which killed some 20,000,000 people.
http://en.wikipedia.org/wiki/Taiping_rebellion
Having nothing whatsoever to do with real Christianity, he managed to single-handedly ruin the credibility of Christianity in China for close to 150 years so far. Truly the momentum of stupid.
But while Hong Xiuquan reigns as one of the all time greats of stupid, there are vast legions of people who do their part to convince both Christians and non-Christians alike to reject and deplore Christianity, often while thinking of themselves as good Christians.
For example, how many sane people do you suspect that Fred Phelps has converted to Christianity? Babbling, corrupt buffoons like Jim Bakker and Jimmy Swaggert? They would have done more for Christianity if they had advocated Islam.
The evidence to this is the real anger seen in many who reject Christianity. This isn’t just learned contempt, but in many it is a cumulative reaction to abusive behavior in the name of Christianity.
How long will it take the Catholic church in Ireland to recover, after some subset of the church engaged in legal slavery of women in the now infamous “Magdalene laundries” for 150 years?
Slaves do not forgive quickly or easily. How many would join any cause that seeks the downfall of their oppressors? Truly a case of the self-inflicted momentum of stupid.