I don't think it is so hard to tell the difference between critical speech and hate/threatening speech just as Seeyou says
I shall illustrate through conversations with my toddler
Me: put on your shoes please
Them: No
this is a normal and fine conversation, I will tell them to put on their shoes and they eventually will (or I will carry them bare foot to the car and put them on later)
But my kids have all been through phases where a conversation will go like this (and bear in mind, they're pretty good kids, I don't need to tell them off much, and I've never smacked them) -
Me: put on your shoes please
Them: No - and if you tell me again I will kick you
This is an unacceptable conversation and they will receive the lecture on how they will not kick, how that is not something you do to other people. Someone - and since their adults, it's going to have to be the police - needs to have a word with these people and remind them that in civilised society we don't go around threatening people with rape and murder.