Courteous or classy, yes - because it's not about denying someone's right to say what they want, how they want say it; but pointing out that there are some ways better than others to say it. Hmm, if that makes sense. The source of wank isn't what people think or whose feelings are hurt, but how they express those thoughts and feelings - not that you should bite your tongue, but that you should take care when you speak.

I don't ever want to be a part of any attempt to try and stifle that kind of reviewing, but if posting a fic publicly means it's acceptable to critique it, then posting a review publicly, by similar logic, means it, too, must be eligible for discussion and critique.

Yes - I think you just summed up my take on the matter in one succinct sentence. (And, likewise, if you are going to criticize someone's critique, keep it classy yourself, else you aren't any better!)