I searched this and it looks like it was already explained over this 6 years ago?: https://www.theatlantic.com/culture/archive/2014/03/a-twitte...
I searched that and the top result was a tweet insulting anyone who even says it.
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Overall that looks like a pretty hyperbolic statement rather than a credible threat.
Whereas "kill Mike Pence" after a group storms the Capitol building sounds a lot less hyperbolic.