What does it mean?"Who are they"?
Yes. Apparently football experts continually explain how the Bengals are not a good team and that the Bengals will have a losing record. The experts always doubt the Bengals. And the Bengals respond with “Who Dey”.
Is that black speech or does everyone talk like that in Cincinnati these days?
It’s called idiotic speech spoken by the blacks and wanna be blacks. Trying to sound dumb is very popular among these types.
Relax. It’s called having fun. The players on the team are employed and they pay taxes. They can have some fun.