I suppose why I find it such a non-issue to me is because I can't relate to American tipping culture. He did his best and he wanted to do something special for your birthday, you might not have wanted anything expensive but he thought you deserved it. I don't know I suppose I would also feel some type of way if the focus was on something negative instead of the nice evening you spent. Also I don't think stopping an argument midway is really something that's healthy, you're just gonna bold up the emotions and that might turn to some form of resentment. As far as tipping I tip based on the service( you only tip at a few restaurants where I live) if the service is lacklustre I wouldn't tip 20% either