Of course it is. Demographics always matter.
I can't speak for the rest of the world but there is data that does suggest there is a correlation between the demographics of MMA/Boxing and race in the U.S.
This study was done on Americans in 2013 but in general, Boxing has been dominated mostly by Blacks/Hispanics for the last couple decades. The demographics of the sport reflects that, not a lot of white American boxing fans but many black/hispanic Boxing fans. In MMA, you have a lot of diversity amongst the top fighters including many white American fighters, and surprise surprise, the demographics of the sport reflects that as well. Most of MMA's fanbase in the U.S. is white americans. There are also a lot of other interesting statistics from the age of fans, sex, income, even how educated they are.
I hope they do another study like this in a couple years, would be interesting to see how things have changed. No doubt in my mind there would be much more female MMA fans than Boxing because of Ronda. We try to pretend race is not a factor but it is, it always has been and it always will. But realizing and admitting that race is a factor is not to say we are all a bunch of racists. Sure, some of it is racism, but overall, it has more to do with the fact that at our core, humans are tribal. Our subconscious is constantly bombarded with cues that identify who is “us” and “them." If an "Insert race" guy is about to watch a fight, but he knows nothing about the two fighters involved other than he sees one is of the same race and the other is not, he is more likely to root for the guy who has something in common with him. That is the casual fanbase in a nutshell.