You shouldn't be able to quit ranked matches. Now, I know that if someone is determined, they'll just quit the game or disconnect, but the numbers would go down if you disallowed it.
On the otherhand, I think quitting in unranked is perfectly fine, particullarily in Stock. I mean, if your the 1st one out and its unranked, why wouldn't you quit an queue up for the next round.
like i said there will always be ragequitters on the game because it was actually made for gamers in the 10+ range. The teen players can easily see this to be true. Just like smash brothers it was a mindless game for younger players to have fun with. They don't have fun, they quit.
This game wasn't made for kids. Kids and family's can play it sure but to be good at this game you won't be a kid. I know a lot of adults who play this game and games like this. I'm 26 myself and have a lot of fun with it. I do understand what you are saying though. Kids play any game and will quit any game but most the folk who quit I find are not kids. Simply because some kids don't care if they loose where as competitive players do.