Henry Cejudo to Conor McGregor, Stop Being a Bitch and Fight Justin Gaethje!

Henry Cejudo says he's "dumbfounded" that Conor McGregor thinks he deserves a rematch with Khabib Nurmagomedov ... telling TMZ Sports the guy needs to shut up and fight Justin Gaethje to prove he's worthy!

The UFC's reigning flyweight and bantamweight champ went off on Conor -- WITH JUSTIN -- saying McGregor is a bad guy who doesn't deserve a title shot without going through a quality opponent first.

And Henry thinks Gaethje is the PERFECT dance partner.

"Yeah, that man likes to sucker punch the elderly," Cejudo says about McGregor ... "Yeah, that man  does terror attacks in our country and he thinks he can get the next title shot with Khabib."

"I know Khabib. Khabib's a man of honor and integrity. Everything that you're not, he is."

"But I got somebody that you could fight, to eventually fight for that title that you want ..."

Enter Gaethje ... who had some tough talk of his own.

"Triple C, the man is not going to fight me. What the f*ck do you gotta do?! He's running out of easy fights. I'm sitting here, smoking my CBD. Waiting for a motherf**ker to punch me in the face. Let's go, quit being a p***y!"

Cejudo added ... "Damn, there you go McGregor. Sign the contract."