Playing is about a team having fun.
This game is a team sport. It is not an individual sport. Even if you play solo queue, you are playing on a pick-up team.
That being said, lack of teamwork ought to get you removed from the mode that you are not playing for the team. There ought to be a team chat at the end of the game, that you have to stay for at least 30 seconds -- to discuss what went wrong, apologize if you screwed up. "It's only _____" ought to be reportable and get a 1 day (from the next time you try that mode) suspension ... rational "it's only ____, then you don't have to play ____."
Upon entering, the 30 second chat, there should be a "remember to report or honor behavior that is outside the norm ... either good or bad." It might encourage people to respect others more if they actually had to interact.
Oh, one more thing, I suppose it doesn't apply to custom games with just one person. LOL