I rarely get my ass kicked in a game, and when I do I rarely leave because i'm only more determined to bash their skulls in. I leave games when my own team is absolutely unbearable to witness. I can't stand stupidity, and I seem to get the random team members that are incapable of doing anything remotely correct.
There seems to be an inaccurate belief that rage quitters and noobs are one and the same, but from experience I find that to be quite the opposite. The low skilled, laggy, nitwits of the gaming community usually do not quit the damn match and leave others to suffer.
Conclusion: I rage at my own team, not at something i'm doing, and rarely due to what the opposing team is doing.