The undefeated boxing legend, who delivered a 10th-round TKO of McGregor in a mega-hyped boxing/UFC crossover fight in 2017, nicknamed his former nemesis "Con Artist McLoser" and attributed McGregor's popularity to racism in a lengthy Instagram post.
"I seen this post and my take on it is that the world knows Con Artist McLoser can steal everything from me and be loved but I’m hated," Mayweather captioned a screengrab of an Instagram comment reading, "Why is @floydmayweather hated for the way he carries himself but @thenotoriousmma is loved for the same way he carries himself?"
"That just lets you all know that racism still exist. Just know, that bum will never be me or be on my level," he said.
In the next section, Mayweather muddled the point by claiming he's actually hated because of his trash talking. McGregor also was once known for unleashing vicious verbal assaults on his opponents while promoting fights, but lately, he has spoken graciously of his last two UFC opponents, Poirier and Donald Cerrone.
"I’m a natural born winner and yes I talk a lot of trash, but every time I back it up!" Mayweather continued. "This is what they hate. It’s sad that you can be a poor black kid from the ghetto that has dealt with racism your whole life and work extremely hard to put yourself and your family in a better position, and most of the hate come from my own people."
Mayweather also commented on McGregor's one-time plan to step in the ring with Filipino slugger Manny Pacquiao in a second MMA/boxing crossover. The prospect now seems dubious if McGregor has any hopes of fighting his way back to the top of the UFC's lightweight rankings in his latest comeback bid.
"Connor [sic] cannot even win in his own sport, but talking about coming back to boxing to fight Pacquiao. Nobody wants to see that, it's like my leftovers eating leftovers."
Meanwhile, Pacquiao praised Poirier after his surprise victory against McGregor.
"Beautiful thing about the fight game, anything can happen!" he tweeted. Congrats to @DustinPoirier."