i think if you're not from an abusive household, you might believe in some mental scoreboard where like, if you're nice sometimes and nasty sometimes, that it evens out. But for someone who was abused, each nice word counts as +1, and each nasty word counts as -1000.
Being nasty to a person who has a history of being abused, even just a few times, makes them cut you loose pretty much permanently. Preserving those friendships requires being thoughtful with your words.