BAR does have a series of scenarios for singleplayer / offline play.

Or in multiplayer you can arrange a co-operative game with humans against AI opponents, which often has substantially less flaming involved, especially when playing a "survive against an onslaught of enemies" scenario.

Also the account system of course allows for muting, avoiding-being-paired-with, or fully blocking players. For more egregious behavior a player can be reported to moderators and temporarily / permanently suspended if they break the community code-of-conduct.