Morality aside...If he was a legend or of great character...I would do it.
Though a good man doesnt cheat on his wife. You sure you arnt in it for the taboo or the thrill of it all? Many men would stick their dick in a faucet if it felt good. Make sure you arnt just a free bang.
Meditate for a short time and be the ubermensch by doing what you feel like.