There were a lot of reasons that Mike was standing there in front of Kitty's apartment. The most important of which was the fact that Kitty was one of his best friends. Even if that label didn't fit quite right, she was important to him and he wasn't going to let a misunderstanding ruin their friendship. He wasn't going to let his evil clone mess everything up the day before Christmas.
He was also there to maybe figure out what he was doing with Kitty. Because even if she hadn't asked and he hadn't told, they probably would need to figure out what they were soon. There was already a lot of confusion about what they were doing and even thought they had agreed to play it by ear, Mike needed direction. Preferably, he wanted to be told what to do, but he would see how that went as he he hadn't decided whether or not he wanted to push that conversation quite yet. In the end, he decided he would see how apologizing went first.
Looking sheepish, he said, "I wanted to say that I was sorry for overreacting."