Does a man touching a woman or a woman touching a man—whether relatives or strangers, young or old, and with any body part—nullify wudu' if done intentionally and without a barrier, even if for pleasure?

Ibn Hazm says that a man touching a woman and a woman touching a man invalidates ablution, provided that the touch is intentional and direct, without an impediment, whether it is with lust or not, and this includes touching mahārim (unmarriageable kin). Ablution is not invalidated by touching from behind an impediment, even if it is with lust.