just my last comment on this - consider that we don't have to worry about precise definitions of defenseless, or targeting or crown, etc. Ask these questions about the nature of the hit - Was it rough? And more importantly was it necessary? If you think that the nature of this hit- launching and going high - was "necessary" to make the football play - i.e. effectuate the block, then you have no foul, but I for one would disagree 100%. The player had a choice to make - go lower, without launching, use his hands, body or even shoulder in a standard blocker motion, or do what he did. I have a foul on this play everytime, or I'd better get a bunch of upgrades to offset my big downgrade!
The unnecessary roughness foul stands be itself without any need to couple it with the targeting defenseless player and hitting with the crown, which are separate fouls in the book.
Unnecessary roughness is a catch-all provision where we exercise our judgment.