Why?

J had been slicing cheese for his lunch for the next day. I turned around to see him with a steak knife in his mouth.

"What are you doing?!?"
"Licking the cheese" (It was hard cheddar, folks)
"You don't lick a steak knife- you could slice your tongue in half"
(ok, a bit hyperbolic, but geez!)
"Only a woman would say that"
"Only a man would lick a serrated knife"