(I'm asking these questions to help the thread grow)
1. Because it subjugates and perverts the teachings of the Rabbi Jesus, adding to his words, twisting them, and making them into another religion, all for the political purposes of Christianity. The most oft-quoted "book" of the NT, John, quotes Jesus AT LEAST 23 times spuriously, according to Bible Scholars.
Why would this cause harm to a person or society? Why try so hard to disprove it?
OK, I'm just a little bit Lost with you now. I was answering your Title Question: "Why would anyone be against Christianity?"
Your "reply" questions confuse be just a tad bit. If you are asking "why would the perversion of Jesus' teachings cause harm to a person or society," my answer is "because it is a perverted lie of person(s) with private agenda(s)." Footnote: I believe that if Jesus was an actual, historical person, he also had a side-agenda: the retaking of Palestine. But primarily the teachings of this entity, if he existed, seem to have been for the benefit of the Jews of his personal world, who were very twisted by the leadership of both the Pharisees and the Sadducees, and especially by the Sanhedrin. I believe that Jesus, if he existed, wanted
to show them how to do it. "Watch me; do as I do" would seem to me to be the best way of describing the teachings of Jesus.
I don't get the next question; please restate.