The kickboxer who knocked his opponent OUT COLD while the guy's back was turned says he's been getting death threats over the brutal hit ... but he's adamant it was a fair shot.
We spoke with Murthel Groenhart about the backlash he's gotten following his Glory 42 beat down on Harut Grigorian ... and the Predator says some people are so pissed, they've threatened to kill him.
But Groenhart stands by his decision to throw the hook ... and even says they talked things out afterward. MG even claims Grigorian admitted he would've done the same thing if given the opportunity.