It really goes both ways. Someone who leaves may be getting forced off the computer and also they might leave on account that they are getting beat. It is unknown.
Unless they track them down, and cut them off from the game for 30 minutes for quitting or having to get off. This is very annoying and dishonorable, and for those who have quit for getting beat whilst in-game, may your dishonorable punk ass get kicked. I don't care if it's a game, it can piss people off.
So, after someone quits a game while still playing, kick them from Toribash for 30 minutes. This easily makes a compromise between the unknown decision of getting forced off the computer or leaving on account of getting beat. Because if you get forced, you're probably in trouble or have to do chores, or have to go somewhere. And that should take more or near to 30 minutes.