I try avoid these type of threads when they get into these type of debates, but...
The problem with trying to rationalize with analogies to other 'similar' scenarios is a difficult one as it really doesn't lend itself to such analogies well. It is difficult, if not impossible to compare things of this nature. Apples and oranges I say. Personally, I'm not offended, but heck, who are we to dictate how others feel or perceive things.
Now to contradict myself and provide a bit of an analogies scenario anyway. Growing up, I had friends who would on occasion use what many would consider very derogatory terms towards Asians. In context, I knew it to be in jest, and really took no offense to it in the slightest. That said, strangers or acquaintances saying the same thing to me would likely not have been perceived the same way by me. Just put into perspective that the audience of the forum is larger than just the more 'active' members and that audience has a right to their opinions and feelings. No one really has a right to dictate how another should feel about the subject matter.
As for religion being open to criticism like everything else, absolutely, but this does not apply to the scenario at hand. There has to be substance to the criticism and a valid argument must exist. Jokes are not a valid criticism. Jokes are simply meant to amuse and or offend on occasion but have no place in a serious debate of religion, politics or the like.
The internet is certainly not a place for censorship so I would agree that if someone truly believes in Jesus being a zombie, than by all means, they should have the right to say so, but lets not make this out to be more than what it is, a joke and not so much a belief. There are plenty of places on the internet to discuss zombie Jesus' I'm sure, though I don't believe the intent of this forum was ever for that. If it was meant to be a lighthearted good willed gesture, than I say have a mod change the title and move on. To tell people to ignore the thread doesn't change the fact that they can still see it and be offended by the title, in spite of what else may be in the thread.
Just my 2 cents.