Who’s going to bell the cat? Our tendency is to hide behind a computer screen, or behind the safe confines of a telephone, to avoid having the difficult conversations.
Don’t hide. Man (or woman) up. Look them in the white of their eye and tell them how you see it. In the short run, feelings get hurt. In the long run they will certainly respect you. You usually win when you call a spade a spade. Upfront. Eyeball to eyeball.