Since I don’t know the poem (I’m weak on Ovid, not having read him since high school dabbling in the Metamorphoses), I couldn’t figure out what the antecedent–and hence the “they” that is the subject of “urunt”–was. I thought it might be some sort of reference to fleshly desires. You are right about Silenus vs. Hef. Silenus is comical (and probably quite aware of that fact), whereas Hef has no sense of humor, or even a sense of joy, so there is something ghastly about his pajama-clad appearance with that lovely young thing (who herself looks quite inanimate, like a doll, because that is probably the best way for her to endure putting up with Hef). Hef was not always this way. Somewhere on the net I came across some letters he had written to his high school sweetheart that were illustrated with his droll drawings of himself and his classmates and teachers. The drawings were sweet, funny, and chaste. There is something to be said for the idea of lust as one of the seven deadly sins; it corrupts and ultimately destroys what is innocent and good.