Mike doesn't understand their situation, since he has left the banquet before Leo asked Clara to sit down the last time.
He really respected Leo and doesn't like seeing him being disrespected. He knew about Sharon as well, because he has helped Leo picked out clothes for the woman before.
Leo wasn't really good with woman then, so he asked for his help. That former Leo was like a friend.
He's very friendly and laugh easily. He even teased him a little when he's asking him if Sharon will like the dress.
Mike knew that Sharon wouldn't mind anything. She's the type of girl who look like she will appreciate rag, as long as it comes from Leo.
Leo thought it's because she loves him very much, which is more of the reasons why he felt so hurt when he found out, she's snaking her way deeper inside his heart, so that she could kill him later.
Sex?