Look at the clip again. The pick-block took place before the receiver touched the ball.
But most important where is the intent to injure????????????? Did Welker cut his knees? Did Welker target his head? No. Welker should sure Belichick for slander.
I'll leave that up to the NFL to sort out. IMO this was an illegal pick, but it wasn't called. It happens a lot in the NFL, which is more interested in protecting offensive players than defensive ones.
Leave what up to the NFL? Collisions on the football field are now illegal? Politically we are in tune but not so much on the football I think. :-}