Why can't people accept that some you can't win some lane matchups?

The biggest problem I face in my current bracket is players that are fking bad losers players, or don't know how to play a game that they can't win lane. The game is just good for them if they have 5k gold lead, and they won't accept any less.

Right now we were Tusk and Slardar vs Winter Wyvern and Abaddon. There were no SHIT we could have done, but the guy kept flaming and griefing because things weren't going his way. Even pulling the neutral creeps was tough because WW Artic Burn is nuts.

He decided by 6 minutes mark to go AFK until the game was over.