First off, let's look at your answer:
I think you should really read Your answer is in another castle: when is an answer not an answer?, written by Shog, one of the Community Managers for Stack Exchange. In this, he says:
Strip the markup, and this is what you're left with:
i think you should take The tutorial HERE! This will help you a lot
Is there even one tiny speck of information there? No. Even the
title of the page being linked to would have provided something to
go on, but that was entirely too much work.
So let me be clear: this sort of response is not an answer. If
you see this, flag it. Moderators, if you see it flagged, delete it.
Yes, your answer was a bit more than just a link, but not much more. The mod who saw this "answer" realized that, and deleted it and left you a comment. Sure, it could have been left undeleted and just had that comment... but is there really a difference? You just flag for undeletion whenever you've improved it. You see, we really can't have bad answers on the site, and might just be left around for days upon days, making the site look bad.
Hence my question: should we accept that our moderators exercize censorship so easily, and without any prior warning?
Shouldn't there be rules of conduct for moderators regarding censorship?
You have something fundamentally wrong in what you're thinking. Censorship and deletion are two different things. Censorship is when it's material that you think the world should know, but the people in charge think it's bad for the world to know that. Deletion on Stack Exchange is simply saying Oh, this is a bad answer or a bad question. If it gets improved, it can be undeleted. However, it's not a good enough post as of now.
Regarding rules for moderators - there are some rules that a mod has to follow. However, the main thing is just use your own judgment. If a mod mistakenly does something, either another mod will bring it up to them or you can flag it as other to bring it to their attention.
For example, I have seen a few answers with rather rude language being
there for long before being edited, and I did not understand why
moderators took so long to edit it (I had myself commented to the
poster that he should edit his post, which he clearly did not care
Again, there's something different you could have done. You could have edited the offensive content out of the post. That's why there's an edit button at the bottom of every post. There's some things that the community can handle themselves, and editing is one of them. Moderators are supposed to be human exception handlers, not the person who does everything for their site. So, if you see something you can fix, fix it! If you can't fix it, and you need a moderator to do something, flag it for their attention.