Knight was right on his analysis of the bad blood.
Marlins resented having their catcher injured with a hit that could have been avoided. Yeah, he was standing on the friggin plate, but still. And when plunked, Morgan basically undid that harm by his steals of 2nd and 3rd. That was a big "FU" to the Marlins, so they felt obligated to continue the one-upmanship.
I found the steals very entertaining. Not exactly dictated by the score, but fun in that it was clear to me that Morgan was making a point. And if you are drilled intentionally by a pitch, that's the proper way to get even, to do it on the field, legally.
I think he could have handled the second beaning attempt more cleverly, however. Maybe just a simple taunt would have sufficed.