Racism and sex can overlap in my view.
If a guy is predominately attracted to certain types of white women, and rarely to any physical/personality types of black women, I
don't think that is necessarily indicative of racism.
However, tone and diction, understood under the light of cultural tones and context can indicate that the wide spread "No Black Men" posters on Backpages.Com is in some measure influenced by some history of racism (when considering USA cultural history of racism). Furthermore, when you compare those American women prostituting themselves to the nationality of Brazilian women prostituting themselves in Brazil. The latter likes or "loves" ethnic Black-American men.
But the kind of ethnic Black-American men traveling and vacationing in Brazil--for sexual tourism or otherwise--are a stable, professional, economically successful to at least middle-class earnings, and probably more often college educated than not. And probably "older" too. These men will comport themselves differently than you younger ethnic Black-American men from the inner-city.
So, the ethnic Black-American women on Backpages prostituting themselves to white men with posters like, "NO BLACK MEN, I Love White Guys," is in part justified. Some of them probably see white men as easier marks when appealing to their egos and desire to be applauded as superior to black men. Others of them have probably had a lot of bad experiences with young black men that "low ball" on prices, refuse to pay unless other "services" are provided, and/or get aggressive and demean them (white, black, Latinas etc) with jokes with their homies. A lot of them--if it weren't for their hustle of prostituting for cash--likely love that cocky attitude from the young dudes. But when it comes to earning their own bread from servicing these young dudes, then it no longer seems so "cool."
But I think some elements of a looooong US history of racism plays a part too.
Consider how many broke brown and black Brazilian men there are in Brazil. Now how often do you hear brown and black Brazilian women ridiculing them as a whole? Just about close to never.
The long standing practice is grown out of the American culture of racism of divide and conquer within the ethnic Black-American population.
So, there are some layers to the Backpages.Com thing.
In the USA it's kind of like this:
Black man = bad. (Even among black men like Obama)
Black woman prostituting herself to white men = good.
Black woman on welfare with 5 kids = good.
Black woman MD = beyond good and into the magnificent.
White woman = good (unless she dates of her sex with a black man, then white men toss her beneath black women in social status).
White woman wanting to be GI Jane = good.
Man destroyers like Kris Jenner (or whatever her name is) = good.
Bruce Jenner as father but become woman = good.
Asian man = good (in IQ and related matters and martial arts but
not as a sexual stud/lover).
Asian woman = good.
White man = good, superb, the standard by which all others on earth are measured against, but simultaneously attacked and ridiculed as the great evil and sexually inferior of black men, by a large swath of modern day feminist and liberals.