Actually, many of them are not. That's the worst part. Many are (according to them) in decent professions, have been watching tennis for decades and write very intelligently.
The young people without a clue you can easily dismiss, but the seasoned, intelligent posters who choose to troll, rather than enlighten is a bit harder to take.
But, I am over it. Sometimes I think these forums are not about tennis per se, but finding a voice, getting attention, and plain trolling for the heck of it.