If someone threatens to "kill all women", that certain someone is nut job, and has no business owning a firearm. I don't give a fugg that he doesn't have the ability to kill every woman on earth. He certainly does have the ability to kill one or more and no sane person would say something like that.
That doesn't mean LE has a right to take anyone else's guns, but they damn sure should take that certain someone's.
Sorry if that offends anyone - actually, strike that. I'm not sorry, GFY...
Then file criminal charges on him and arrest him.
Pretty hard to carry out threats when you are in jail.
Due Process MUST be preserved.
If ANYONE doesn't agree with Due Process, they can in no uncertain terms GFT.