It might depend on who's doing the arguing, but for me at least you misunderstand the argument of "society is to blame". This absolutely does not absolve such people of any responsibility at all for their actions. They can, should and must be found and brought to justice. But at the same time as all that we ought to try to understand what led them to think of such actions as normal and even fun. Is there any role of society as a whole in it? The answer is generally held to be "Yes" -- because, say, an entire group of people is ignored by the rest, not given the attention or resources they need, treated as some sub-class. Such treatment can be a self-fulfilling prophecy. If you keep telling people that they are somehow sub-human and not fit to live in civilised society they might start to believe it. And then those who spread that message can sit back and go "told you so" smugly, but in the meantime nothing changes except for more people believing they do not belong and reacting accordingly and with violence.
There is more to it than this, of course, and I'm speaking in general terms rather than abut this specific case. But if you start from the not unreasonable viewpoint that everyone (at least, almost everyone) ultimately wants safety, security and peace and quiet, then presumably something must have gone wrong for people like this to emerge so often. Then you can try to understand what it was and how to discourage it for the future, while also dealing with the problem in the present.
I suppose the short form of the argument above is that those who say it should be only the carrot are as wrong as those who insist on using only the stick. You need both.