Yes, if your morality is arbitrarily determined by what you can get away with, everything's moral that you can get away with.
Does the father in a particular family get to set the culture of that family? If so, I think that many child molesters may have the basis for a "common sense" appeal through your argument.
Everything you said here is nonsensical and wrong. You completely missed the point and are rationalizing your own culture as the only right culture.
Treat culture the same way you treat religion. Just as there are many religions, but none of them is the right religion, so there are many cultures, and none of them is the right culture.
As for your attempt to label the father as child molester in this case, you are wrong. Child molesters are people who not only are showing behavior, that is unacceptable in the culture they are in, but also they are doing it, at least in some cases, against the will of the partner. What the father in this case did was nor against the culture in which he did it, neither against the will of the partner.
Does the father in a particular family get to set the culture of that family? If so, I think that many child molesters may have the basis for a "common sense" appeal through your argument.