How do you explain to a blonde that a coworker has a wife at home and is a good family man? She just doesn't get it! It is easier to cum in her mouth than to explain it. So his conscience can be calm - he did not cheat, he just bought the girl a cocktail. And he put it in her pussy just to make conversation - fuck me, das ist fantastisch. Let the blonde think it was her charm that worked and make her feel happy.
Everyone has their own way of persuading to do something, and sex is a very original option. The important thing is that the father was able to talk his daughter into learning, and the contact brought satisfaction to the couple.