This type of fashion does come from prison. When you first go to prison and get a uniform, the guy taking down your measurements (another prisoner) will say something like “Okay, you’re a 38 regular? One pair of 38 regular, coming up!” and give you a 50 inch waist just for the hell of it. It’s what happens to ‘new fish’.
It is not really connected with prison rape, but like the previous commenters said, if you’re as obsessed with something as Scott Lively is about anal sex, then you’re going to see signs of it everywhere.
[Incidentally, another type of fashion that comes from prison is the ‘do-rag’ tied around the head. Headwear cannot be imported into prison, but the do-rag is easy to improvise from a torn-up sheet or whatever.]