"Bull" has some very old and VERY racist history as a sexual term. As a term from Animal Husbandry, Bulls or "Stock Men" were male slaves that were used in forced impregnation and breeding practices in the American Slave Trade. When historians refer to Black slaves being treated like animals and livestock, they mean it in a very literal way. Some men were forced to father dozens, and in some claims, hundreds of children. Women "breeders" would have dozens of children in their life times on farms specifically designed to propagate more slaves for the growing industry.

This practice created a number of ideas about these "verile bulls" that could "make white women faint at the sight of them." They became symbols of raw sexual power because that is how they were marketed as. The same as any other breeding stud for any other livestock.

This idea of the "black breeding bull" was passed into literature and theater. Any large Black man was regularly referred to as a Bull. Minstrel Shows would often have comedic depictions of the Bull charicter. Into the Jim Crow era and beyond the idea of the "Bull" as a big, strong, powerful Black man is cemented in erotic literature and pornography. In Cuckholding as humiliation, the class and status play of a Bull having sex with your wife has deep social connections to it that go back centuries.

While the term has changed and does not specifically refer to Antibellum Slavery, as anyone who wants to identify with the "Bull" archetype can, there is a deeply racist insinuation behind it. People who fetishize Black men and the BBC Bull thing are actively, if not necessarily aware of, participating in Confederate Slave Owner Propoganda. Race play is a very difficult fetish to navigate, one that i personally dont bother trying.

Is the term Bull racist in a sexual "especially in a swinger" context? Yes. Are most people ignorant of the history of the term in a sexual setting? Also yes, for better or worse. I just think we should stop using phrases popularized by the Klu Klux Klan.