I think you might be conflating the terms "troll" and "asshole." If you show up to a subforum on SA and start actually trolling people by posting spam or a bunch of NSFL images or something, you'll get banned pretty much instantly.
That's not trolling, that's vandalism. Trolling is posting things for the sole purpose of inciting flamewars, or getting people to believe you were serious and react with disproportionate fervour.
