To be honest, Christianity and the figures therein are much too widespread to be protected by a no-joke taboo anymore. It's basically public domain. And anyways, Jesus and the like are historical figures, and as such are not exclusive property of any religion. I don't know about anybody else, but I'm not going to tailor my speech to cater to the sensibilities of anyone should I deem it unreasonable to do so.
Try using that logic with a Muslim the next time you draw a funny picture of Mohammad. The reason it's "ok" to bash Christians is because they won't commit acts of terrorism against you.