What am I supposed to make of this thread?

Is it at all possible to have discussion that involves Christianity (or any other religions) without forming tow camps that call each other "intolerant, ignorant bigots"?

This thread is based on Nietsches statement that
"Christianity [...] has been the greatest misfortune of humanity so far."

This certainly goes beyond stating that he does not believe in God/a god - it rather is a direct accusation brought forward against Christianity and is as such of course rather likely to get a reaction.

Do I think it should not be allowed to quote such statements on this board?

I do not - as banning this kind of statement would be equivalent to suffocating half of the discussions on this board.
I think we had countless threads that had articles, commentaries etc. that made these kind of generalized statement - that a certain idea, be it Islam/Christianity/Socialism/Capitalism is bad for humanity.

Attacking (meaning "attacking in a civilized way") an idea is often the subject of discussions here - things get problematic when criticizing an idea turns into personally attacking or slandering the people who follow that idea (I am aware that the line is fine here).

However, if you post such general (and in the Nietzsche case not backed up) attacks on an idea, you should be prepared for others to in turn attack the statements you posted.

Short version: I expect any participants in this thread and others to refrain from personal attacks and discuss the issues