Getting barred, and foul language

My 8yr old son enjoys playing minecraft, I thought it was a normal and safe game for him to play, however, earlier on he got barred, and the message stated “you’re barred, so fuck off” is this the norm from minecraft?? I dont know what he had done, but this was very extreme in my opinion, and not the language I want for him to be reading on here, believing it to be a safe game. Why is this?