Sielle: What are your personal views about the crusades? If you think they were a good thing then I'd avoid the game.
Phosphenes: I don't really know that much about them or have any opinion on them. I just mean is the game really anti-christ or is it like a historical thing?
Not anti-christ so much as anti Knights Templar and how some people will use their influence within the holy sea to further their own ends. Yes it does portray some of the popes as evil (which if you actually read your history books would be hard to disagree with) but it never attacks any religion directly.
Assuming you're somewhat open minded and not a blind zealot then nothing in AC1 or AC2 should offend you beyond "Oh man, do they have to remind us that Christianity actually did do this?"
StingingVelvet: It's not anti-Christian at all it just portrays the crusades as evil (which they were).
Don't forget Pope Alexander VI in AC2.
Phosphenes, if you read this
http://en.wikipedia.org/wiki/Pope_Alexander_VI and think that he and his family were a good example of upstanding Christians then you should probably avoid the AC series.