@the OP -
Christianity is, of and in itself, not evil - no more evil than the code of the local Rotary Club or Moose Lodge.
The problem is that Christianity promotes ignorance, by placing all knowledge in the hands of God; it encourages the idea of "if I do not know, then God", or "if I don't know what to do, then God", or (even worse) "as long as God, I don't need to do anything." Because its practitioners are encouraged in ignorance and rote obedience, it does not evolve well. Currently, various sects of Christianity (and not fringe ones, either) promote the subjugation of women, the removal of individual liberty on nebulous moral grounds, racism, classicm, victim-blaming, victim-shaming, witch burning (no, I'm not kidding), sufferance of abuse, and worse besides - relics of a time when these actions were arguably vaguely more enlightened than the 'kill 'em all' attitudes that persisted before they were brought to the table.
Gay marriage? Biblically opposed - nevermind that two people who care about each other are basically excluded from public services, rights, and responsibilities simply due to gender in the civic (non-religious) space. No, the bible has problems with it, so the country can't allow it - ignoring the perhaps quarter of the population that isn't christian, and the further third that isn't evangelical (and thus doesn't agree). Slavery? Biblically supported. Segregation? Biblically supported (and, amazingly, they're using the same arguments now against Gay marriage that they did against interracial marriage!).
Christianity claims universiality - what's good for christians is good for everybody... and that's the problem.
So... yes. Christianity is evil, or promotes evil, because it promotes the things that feed evil: "us vs. them" thinking, ignorance, blind obedience, 'one-size-fits-all' moralism, and an inability to accept that you don't have to force people to conform to your moral structure in order for you to have that moral structure. It adds to that a healthy dose of persecution mentality and martyrdom... and the seeds are sown for all sorts of horrible behavior.