What Carly and Michael did had direct impact/ramifications for Sonny. We are in agreement that what they did was worse--which is my point. The punishment doesn't fit the crime for Nina and is totally inconsistent with Michael/Carly's crimes!
Perhaps it's a simple as she's his wife but then he needs to state that and he hasn't because you know--he won't even talk to her. "You are my wife. I can't be with someone I cannot trust." It's not hard. He just had to use his words. But to me he looks really silly and fickle here. I mean one lie torpedoed his marriage.