The important point is not "hate", but "in public": You are free to believe whatever you want in private, you are free to talk with your friends about it in whatever way you like. But when you do this in public, with the possible (very likely intended) consequence of making others use violence against some group (usually a minority), than this is bad.
So the intention of the law is to protect the victims of the violence before the public incitation can reach a point where they become victims. Because that's what happened during the Third Reich in Germany on a large scale (and it's still happening everywhere on the world).
In other words, your personal freedom (of free spech) ends where it starts to violate the personal freedom of other people (bodily harm via a third party). That's different from the American view, which somehow has glorified free spech as an absolute virtue, and doesn't care about negative consequences.
So this law is not about violence at all (which is also punishable, by other, very different laws). This law is about public behaviour. And if a case comes before a court, the court won't have to define "hate", the court will have to decide "is this public behaviour which can serve as incitation to violence against others". And in a case like "seven people were beat to death in India after a false viral message on Faceback", it's probably pretty easy to decide. In other cases, it will be harder, but that's what courts are for.
And a big problem of course is that the internet is blurring the distinction between public and private: Before the internet, you'd need to print and distribute flyers, or manage to get an article in a newspaper, or book a slot on TV. That's costly and not open for everyone. Now, you can just write a message on Facebook at no cost at all, and millions can read it.
The law has to catch up with this problem somehow, to protect the victims. In what way the law needs to be modified to deal with it remains to be seen; but it should be obvious by now that the big actors like Facebook have no interest in dealing with this problem on their own, without prodding.