The UFC superstar says he's seen our vid of Conor clocking the bar patron for rejecting his whiskey ... and Miocic has gotta give props where it's due -- saying the guy soaked in that hit like a pro!!!

"I give that guy a lot of credit, he ate that [punch], too," Stipe says ... "amazing."

"I was like, man, that guy's got a chin of steel."

Miocic is reserving judgment on the situation, though ... saying he'd want to hear both sides of the story before calling out McGregor for the hit.