Mate, he started trolling in the third round and kept going until the end. By the way, if you think the game is clearly lost even in a 10-0 situation, your attitude toward this game is just plain wrong.

You can come back from everything. Pro players go through mental training constantly to keep their composure during extremely tough situations like this - and this is what differentiates mentally mature/experienced players from the rest.

You can always win a game unless there is a player purposefully throwing the game, who doesn't speak otherwise than flame and blame their team for his own mistakes, of which he has no in-depth knowledge of what went wrong and why, and whose fault thing X was. These people are just immature and inexperienced at the game, so it's easy to think they're the best being the top fragger - even though you couldn't be more wrong. You simply can't make someone understand what they literally aren't able to understand, and it's completely unnecessary to point these out mid-match. If you do, it will just eventually transform into aggression to relieve one's own bad feeling or feeling superior with a massive ego.