When clients command you to do things?

Just saw a new client. Giving him a bj he's like "grab it harder." (I try to) He's like grab. it. harder. Im like excuse me? He repeats himself, in a tone like he's scolding a dog. I'm like you need to talk to me respectfully, you're being rude. He's like I didn't mean to, I just like it grabbed hard. But I know he was being disrespectful, I'm not an idiot.

What do you say when clients do this shit? Do you just let it slide or say something?