It started when a nice guy hundreds of years ago pretty much said, "Hey guys, maybe we shouldn't be assholes to eachother." For this, he was nailed to a tree.
However, everyone didn't seem to be able to understand "Be nice" so they made up a ton of reasons why he said this.
Eventually this was spun out of hand and one question led to another.
Eventually it started being used to give reason to biggotry. Such as hatred twords gays. When the real reason that these christians hate gays is simply because they are different from them.
It was mainly used to squeeze money from followers (similar to Sceintology). And to gain more followers the christians decided to smear other religons, like Saitanism, to have more followers and more money.
They did this by naming the guy they blamed everything on Saitan, putting their nonsense holidays on the same days as other holidays, and even taking over the holidays of other religons (like Christmas).
Today it is used for, the mental controll of the population of America, stealing money from it's followers, making hate laws (no gay rights), making yourself feel better than everyone else because you belive the story about the cosmic jewish zombie who is his own father, etc...
There are too many christians on the interent.
"No, I'm pretty sure it was Christianity that started WWII."