Oh wow, that's REALLY helpful. Let's just accuse someone of lying because we don't understand why this has happened to them and are too lazy to find out, but are also so egotistic we feel the need to comment anyway instead of just staying shut up.
OT: Unfortunately, there's not really anything you can do about it. Longtime loyal fan or not, you've got to consider that what you do in-game affects other players, too: other players who've paid just as much money as you for this particular game, and who are just as entitled to a good round of matchmaking as you are: by quitting, you're hurting that experience for them, and while the resulting ban is probably on the harsh side, it's a pretty good deterrent.
Sometimes life does get in the way, and that sucks, but at the end of the day all you've lost is an hour of a video game that will still be there tomorrow and the day after. Plus you've got to remember, it's much better to have a system where you can't basically just bribe your way past the rules than one where giving handing over money gets you an advantage. Just because you've been with Halo for a long time doesn't give you the right to hurt someone else's game: how would you feel if every game, someone on your team would quit leaving you a man down, and that these people wouldn't be punished just because they'd spent money on it?
I've also heard that there are much harsher bans for quitting multiple matches in a very short space of time than it if you quit often, but fairly spaced out. It's possible that you've just fallen afoul of one of these bans: if so, it probably won't happen again as long as you try not to quit multiple games in a row in the future.