If you have ever used that to insult a person then I question your insulting ability.
Insults work best when you say that someone is a bad thing and most people like the smell of Reese's Peanut Butter Cups.
That's why so often you hear poop or fart slurs when it comes to insults. Very few people want to be a poop or a fart.
Frankly, I'm a little surprised that something this obvious needed to be addressed. But there you go.
You smell like a Reese's Peanut Butter Cup . . . eh.