Yes, you're correct; alcohol impairs judgment. But it does not have amphetamine-like properties. I've been around a LOT of drunks and dopers at my job. I'm a pro. ;)
I didn't see him restraining her. She's not a big girl, but he was speaking to her calmly, holding her with one hand, saying, "I can't finish your tattoo unless you're still. Be still," and guiding her with his hand. Trust me, if he'd really restrained her and forced her to get a tattoo, she'd own that shop.