The best way to make it easy for the low-brow followers to kill the enemy is to dehumanize it. That is what right-wing talking-heads have been doing for a while. Of course, if someone actually gets killed, they did not do it - they were just telling "jokes" on radio or TV.
My understanding is that the term "posthuman" was used by 90s techno-libertarians and cyber-Utopians and meant to be positive - self-directed evolution freed from the constraints of nature, part of the faddish smart drinks / virtual reality / body modification zeitgeist. (Chronicled in books like Mark Dery's 'Escape Velocity.') Later, the term was adopted by social conservatives, who related it to CS Lewis' 'Abolition of Man,' as a warning about biotechnologies and changes to core institutions.