It's really best to not reply to the mentally ill people (and you can be pretty sure anyone sending something like the first is at least temporarily mentally ill).
It can sometimes be extremely tempting, I know-- especially when they've managed to say something almost perfectly constructed for pithy comeback. But it will not help you and it will not help them. If it does anything it will just encourage the behavior.
If it is any consolation lots of other people receive nasty kookmail messages -- I know first hand, in addition to the ones I get directly some of the kooks like to send massive carbon copy blasts-- as a result I have a bunch of very strange mail rules, like discarding any email that copies both a whitehouse.gov email address and Jeff Bezos, or another if both George Soros and Noam Chomsky are copied.