This bib's maker calls it a "rivals bib."
I'm a fan of a certain team, not the rivalries associated with that team. They're rivals because we hate them. If I'm gonna wear a kid's bib (i'm a messy man in my mid-20s), I'll wear a full-on Steelers one. I don't need to be reminded of John Madden's fat, or the Raiders beating Pittsburgh in 2009.
Show me a Steelers/Browns one and I'll vomit all over half of it. On purpose.