USCe vs LSU penalty

I do not have a dog in the fight between USCe and LSU.
I realize that when a QB throws a pick he goes from being a defenseless player to being a potential tackler.
And I bet guys used to be (and maybe still are) coached, "If there is a pick, find the QB and knock the crap out of him because he is fair game." I think when there is a pick, officials will look for someone blindsiding the QB.
Kennard hit him with his hands, but it was a good lick that laid...

USCe vs LSU penalty