My (adult) son likes to sing and thinks he is talented but actually his singing is awful and he sings all the time when he's home, wandering around the kitchen singing at the top of his voice with his very deep out of tune noise singing.
I don't want to offend him but AIBU if I tell him to STFU and stop singing even though I know he sings because he's always in a good mood and it's me that's the grump.