People toxic even in a bot game?

Hello everyone, Why are people toxic even in a bot game? like really, my friend and i just wanted to play a quick bot game just to finish a mission then off to sleep for summer school. For the record the player was playing brand and i was cassio laning at bot. During the game he starts to tell me what to build and how to play because he said he is "diamond" then i just told him i didn't want any advice that i already knew how to play. But no, he started to become toxic out of no where saying he is "married, has a wife and child and that he has a life". Even calling people retarded like really dude? Then my friend and other players in the game just start defending me. After the game, after the reports, I start to think why are people toxic even in a bot game? [removed by moderation] this is a picture of the player, his real account is fake.