It was a punch. And all the talk show hosts were on the next Monday, defending Koroma by saying that you're supposed to "jab" a D-Lineman in the gut when he jumps to swat a pass. Koroma was doing that - he was jabbing at a jumping D-Lineman. Unfortunately for him, there was a big enough gap in the line of scrimmage that both the ref and the camera got a clear view of what happened.
Doesn't make Memphis' behavior okay. I'm just saying that it's not really reasonable for a couple of guys to jump someone for no reason...