Khorn doesn't hate psykers and sorcerers, he hates their preferred method of combat. Where a psyker will think you to death with mind-bullets, lightning, telekiesis, etc, Khorne would prefer they stop thinking and rip the bloody guy in half with his hands/weapons. And then he tolerates psykers who worship him (see Gaunt's Ghosts book Blood Pact, featuring a psyker member of the Blood Pact, who all worship Khorne).

Also, Hi, I'll be your Imperial GM. [i]Imperator Protegit[/i].