I believe Suh is a dirty player in general but on this play I am not seeing it clearly. I think this is a genuine attempt at a football play; stomping on offensive lineman and throwing QBs around after the pass are what I think of as clearly dirty play.
Yes, the block was illegal and, with the benefit of an overhead camera and hindsight, unnecessary.
But you can block the QB on a return, and in fact it is often done. Here's the rule:
In practice, unless the passer stands stock still or starts walking towards his bench prematurely, he's considered to be in a defensive position.