Perhaps the Admiral gave Henry a lot to live down to.

I mean that quite seriously. We know that the Admiral was a man of "vicious conduct" (ie given to vice) and it seems, from his wife's unhappiness and the way he made Mary homeless by moving his mistress into his house, that he just doesn't care about hurting women's feelings. I'm wondering whether growing up with such a model of masculinity has made Henry think that this is how a "real man" behaves. Boys are sometimes unconsciously in competition with their fathers, so maybe at some level Henry even feels the need to out-Admiral the Admiral, so to speak.
This is just a guess. Casanovas I can understand, but I don't really 'get' what makes men like Henry tick.