This is where I've historically been. And where I generally land, regardless.
But it's similar to how I respond to people in life - if someone attacks me verbally, I'm going to walk away. If however, they attack me physically, I will respond in kind - regardless as to whether it's considered 'right' or 'wrong'.
In this case, if a player is taking an obviously cheap shot at the QB in an attempt to injure him, I'd call the refs over,and point out he behavior, letting them know they'd better deal with it. If they did not, I'd target the opposing QB in similar fashion.
Call it right or wrong, but I'm not letting people injure someone cheaply like that. It could literally end someone's career, so at some point you confront it.