I agree, sounds like a frustrated father dealing with an ex wife and a child who’s not behaving as well. Classless yes, but frankly, having seen what divorce and such does and behaviors out of adults and children involved in them.... I’m not going to condemn the guy to hell over this.
Frustrating as hell when your authority as a parent is undermined by another parent, and you are thousands of miles away as well.
He's an adult. There's no excuse for speaking this way to a child. Period. End of story.