Mayweather's comments are not some big revelation. Of course there is racism in combat sports, and it is sickening. There is racism in every sport, all of which is sickening. As a problem with society-at-large, it is going to permeate society's many institutions, including sports.
Unfortunately for him, Floyd is one of boxing's biggest racists, and the comparison to McGregor is silly. And, look, this is coming from someone who loves to watch PBF box and generally detests UFC, including McGregor. The financial success of Floyd's second-to-last fight alone completely eclipses anything McGregor has ever (and likely will ever) accomplish.
Let me paint a picture: McGregor talks shit, some people cheer, some people boo, he wins, collects a paycheck, laughs on his way to the bank; Mayweather talks shit, more people cheer, more people boo, he wins, collects a much larger paycheck, laughs on his way to the bank. Everything Conor is doing, Floyd does to greater attendance, viewership, and monetary gain. His false distinction of, "Me and McGregor act the same, everyone loves him because he's white and hates me because I'm black" is simply not reality.
To the extent PBF is vilified, it's often due to his actions outside of the ring, the most notorious being his habitual physical abuse of multiple women, the details of which are public and disturbing. Apart from the most recent reported instance, he always escaped meaningful punishment. As a lawyer whose spouse is a former criminal defense attorney, the legal ramifications for his actions were atypical. How is that for a double standard? Public opinion of this type of behavior is understandably negative. Of course, as far as anyone knows, McGregor could be doing the same fucking thing day in and day out; the difference being, no one does know, as he has no reported history of similar behavior. The guy acts like a jackass, without question. but also doesn't have the reputation that comes along with repeated acts of domestic violence. It's really pretty easy: you beat women, people call you a scumbag; you haven't beaten any women as far as anyone knows, people don't call you a scumbag.
Lastly, and most ironically, Floyd's claim of not being racist himself is almost comically false. For all of the instances he has decried racism in combat sports, I can give you two instances of him saying blatantly and disgustingly racist remarks about others.
So, yes, Floyd, there is a racism problem in combat sports. What you seem to be missing is that you are a part of that problem.