It's not about censorship so much as it is about not abusing members. WebDiplomacy is (and I think probably diplomacy sites in general are) experiencing a strong growth period. Our forum is part of the front page of our site, seen by *every* single member. Right now, we have nearly 2000 members playing games. This is fantastic!
Remember that we are first and foremost a place where people come to have good, high quality games of Diplomacy.
In order to keep these new users (and to have the best, most varied games that we can) - and in order to have a happy membership, it's important for webDiplomacy to be a welcoming place. Having threads on the front page where members are abusing other members for religion (or whatever - it doesn't matter what the content is) does not move towards that goal. In this case, a member complained, the user was asked to tone it down, and instead, he took it to the forum. Having a discussion about censorship is all well and good, but I don't think it's censorship to be told "please keep your discussions respectful", nor do I think the posts in that thread were intended to start a respectful discussion about censorship.
The rules are available for everyone to read here: http://webdiplomacy.net/rules.php In particular, the common sense rule *literally* says please "use common sense and respect other players".
You mention that discussion can't be had without being allowed to say whatever you like - as an example, have a look at
threadID=1249317. In this thread, Maniac says he's standing for a particular political party, and among the congratulations and good luck comments that Maniac receives, there follows some strong disagreement with the policies of the political party. Despite the disagreement, the discussion was generally respectful. It's clear that abusing members is not a requirement for lively and interesting forum discussion.
For the rules-lawyers amongst us - although I am a moderator, this isn't an official moderator response. For mod team responses on things like this, we typically have an internal debate first, but most of the mods are offline right now. This post represents my views as a member, not the views of the mod team.
We're all here to play Diplomacy. Surely we're able to be diplomatic - and respectful - on the forum.