Its actually easy enough to deal with. Understand that any compromise only leads to their next attack and stop making compromises with them.
You let them throw tantrums like you would do with a child and then you let them face the consequences of their tantrums.
I don't have kids, but my mother swears that the best way to stop a tantrum is a little bit of water thrown into the child's face. They may gasp and sputter, but they'll quit screaming.
Of course, a Leftist would claim they were tortured by water boarding.