You're off-base. Derrick Lewis is very well-liked (though considered faintly ridiculous) and he's “the Black Beast”. People are also mostly rooting N'gannou despite (and partly because of) the fact that he's giant, scary and African.
Cormier is liked by most, as is Rumble (inexplicably, given his domestic abuse conviction).
Rampage and Rashad are both broadly popular, too, although Rampage occasionally grates on fans with his bullshit and Rashad is considered fairly boring.
Anderson was disliked for being a smug showboater in his prime, like Ali, but is well-respected now that he's a fading veteran, also like Ali – is normal.
Jacare and Yoel are pretty much universally popular.
Need I go on?
Prominent black fighters who are disliked, like Overeem (who I actually enjoy), Jones and Woodley, are all disliked for very specific reasons.
Overeem because he looked great shirtless and it hurt people's feelings (it wasn't the PED abuse; his opponents were almost all known juicers and none of them caught much flak for it relative to Overeem).
Jones because he's a terrible person.
Woodley because he's boring and entitled, and because there are some sour grapes over him KO'ing a fan favourite on an undeserved title shot and then refusing to fight the clear number one contender afterwards.
All in all it's pretty clear that the whole “unpopular black fighters are unpopular because they're black” thing is untrue.
Jones attracts no more hate than Rousey did, Woodley attracts no more hate than Hendricks did, etc.