I don't have a problem with anyone who leaves a game early because of an impossible to win scenario.
Who decides what is an "impossible to win scenario"? You? What if you're wrong? What if you could have won, but since you left now it's impossible for the remaining people to ever accomplish?
So what happens in demigod because of this attitude? SomeRandomNewbie starts playing demigod. He doesn't come from DOTA or wherever the hell this ridiculous attitude spawned and sees no problem with leaving when the winning team has an irreversible edge.
And now he's ruined the game for each and every other person in it. He *should* be ridiculed.
The critical problem in this train of logic is that you are only caring about yourself. *I* don't think we can win. "My" fun. No. The moment you started up a multiplayer game with other people you made a committment to both try your best to win but also to stay the course. You don't start up a game of Dota when you know you're going to have to leave in 25 minutes. That just disrespects every other person there.
If you don't want to deal with this responsibility there are innumerable great single player games on every gaming platform you can play instead. Online multiplayer - it's not about you anymore - it's about the team.
If the team agrees that the game is over and they're giving up, sure, now you can leave.
If Newb X comes onto Demigod with a "it's all about me, I'll quit when I want" attitude towards multiplayer games I have no problem if he is put off by the "elitist" community and leaves in disgust. After all, he would have never been a part of that community to begin with.
This "ridiculous attitude" was spawned in the first game that ever featured the ability to play with people you don't know, and every game since.
In my experience, nothing ruins a game worse than a leaver at the worst possible moment. You'll never know if you could have won, because now it is impossible. It's worse than losing. And winning against a leaver team doesn't feel good either - a hollow victory.
Leavers are worthless. You won't get better at the game by leaving. I have no sympathy or pity.