It is absolutely unacceptable in every single way, and a tremendously awful PR and ethical decision by the NFL to allow that to happen.
Listen, I'm not naive enough to say that the macho-attitude of the NFL is a good thing for player safety or helps the league in terms of its perception.
What I'm saying is, the way the game is played, I can see how these things would happen. If I pay a guy $50,000 to blitz off the edge and hit the QB in the back as hard as he can to knock the ball out (which is what players essentially get paid for in their contract), is that any less or more acceptable? If I teach my smaller defensive backs to dive at the knees to tackle a bigger running back, or if my teach my huge offensive lineman to throw their bodies at the knees of a linebacker to stop backside pursuit and cut them, is that any less or more acceptable? If my wide receiver is taught to come down inside and blind-side a safety who's chasing the run and crack him, is that any less or more acceptable?
I posted this video earlier, but notice all the cut blocks and bodies on the ground after this carnage. What makes this acceptable? Because nobody had "intent to injure"?
Alabama's Mark Barron levels Vanderbilt's Jordan Rodgers 10/8/2011 - YouTube
Where is the line? The issue here is that they threw the word "injure" around. But all of the acts mentioned above happen on a regular basis, and in each case, players are at risk for injury.
When does a "good technique" or a good "football play" (the worst phrase in sports) turn into a malicious attempt to hurt someone? Is it because they said it, or is it because it happened?
I think in both cases, the players on the field respond the same.