Grandma's gone to bed

An expression used to hint that a certain idea is obsolete and anyone in their right mind would retire it immediately.

Person 1: I heard all gays are pedophiles too.
Person 2: I don't think anyone's believed that since the 60's.
Person 1: Really?
Person 2: Yeah. I think grandma's gone to bed on that one.

selling point

An aspect that is stressed when selling a product or service to others.

"This cute guy asked me out, I wasn't gonna go due to Hair Migration, but then he sent a vid of his puppy."
"So... the puppy was the selling point?"
"Yeah. I guess the guy's surplus, but I'm such a sucker for dogs."