What Drac said.
people either leave or get banned because they either don't want to or can't abide by the rules.
IN MY OPINION:
You beat me to it. I was going to say this, and it's an important distinction. Some folk can't help themselves, some won't help themselves.
TJ fell into the former category. Even at the end he was posting comments to the tune of "I can't get drawn into this" and it was fairly clear that he didn't really get what he was doing wrong. If he were to come back and not argue that black was white at the drop of a helmet he'd probably be allowed back. But it'll never happen because he just can't help himself. Which is a shame, cos when he put his mind to it he was a clever bloke and a valuable contributor.
Fred fell into the latter. He knew full well what he was doing and just didn't care, he was doing it on purpose. His parting shot emails to us burned his bridges, the absolute contempt he demonstrated means that there's no chance he'll be allowed back without a full and sincere apology. And I'd hazard that's even less likely to happen.
*even* moderators like Drac and Cougar have bad thoughts sometimes, but they keep them to themselves. That's what everyone should be doing.
I'm having one right now.