Steam ID: STEAM_1:0:41091287
Lobby ID: #925869
Dude got mad at the video game and joined the enemy team, forcing my team to play 7v5.
Dunno if it is a bannable offense but I think it was a dumb thing to do and it ruined the game for the rest of my team - and probably for the enemy gamers as well.
Proofs can be seen in the logs + chat logs.