It is peculiar how intensely the internet can affect people. Imagine we were all together in a room with a piano instead of posting on a forum. As I have said several times, I have been at many gatherings with enthusiasts of very widely varying musical taste, philosophy and temperament. Everybody plays the piano, talks, sometimes argues quite vehemently, has a few drinks, a good time and departs happier for it.
I think the time element has something to do with it. The immediacy of response in person is removed and posters have time to brood about things they don't like and magnify them in their own minds until they assume an unwarranted importance. I fell into that trap once, but after not posting for a while I realised how silly I was. Nothing on forums matters that much really, after all.
Mind you, I think spending too much time on the internet generally is not a good thing, and I have reduced my posting time on both piano forums considerably. But that is just time and common sense, not a consequence of something someone has posted.