Why ?

Because, it is one thing to discuss, question and eben debate other playstyles, but those types of comments evolve into other one-liners like..
I really should leave this thread, immediately.
I know that some of it is just comradery. I am guilty of that myself, but my posts follow up with smilly faces and or additional posts to explain the comment of being in good fun. Others actually come to expect that from me and take it with a grain of salt. Then come back with something witty.
When you oneshot like that with a newer member, they can be taken back by that.
I use to be a "do-all" type of player, until these forums, namely Oblivion, opened my eyes and made me a better player. That was through extensive dialog and not shoody one-liners.