"You don't find face slapping a turn on, do you?"
"No, M. Not really. It's not something I'd seek myself.''
''And yet you asked me to slap you. The other day. Why, if being slapped doesn't do much for you?''
"Being slapped doesn't turn me on. But slapping me turns you on and I love that."
And that he asked for it even though it wasn't his thing turned me on even more, of course.