I saw the first few seconds of the video where the guy/kid has his hand around the cats neck and I stopped watching because I knew I wasn't going to like what I saw (I have two cats, love animals and really can't stomach cruelty to animals).
In short, the person is low life scum. I'd happily kick him in the nuts for what he has done and I think he needs professional help and dealing with by the Police/RCPSA.
However, things like this (and much, much worse) happen daily. No outrage from the masses. I'm not sure what the punishment is for this type of animal cruelty in the states, but I can bet it's going to be a lot more lenient than what he is about to receive from the bandwagon jumping e-vigilantes/keyboard warriors.
I think what he has done is bad, but what others are doing in return can be seen as much worse. Surely the correct thing to do is have him dealt with by the proper authorities and let that be it, it sucks and maybe lenient, but that's life.