I'm a bisexual white man and I've been on all four sides of the racial dominance equation, I've been submissive and dominant with black men and women many times. For the purposes of your question:
When I'm submissive with black men, I feel freed in a way, as I'm able to step out of my social and sexual role as a dominant straight white male who, at least historically, is a prime example of the sort of person who has been at the top of society for generations. In submitting sexually and devoting my body to pleasing black men, who have historically occupied the opposing social space from me, I sometimes feel a sort of spiritual "rightness" as though both me and the man who is using me are engaging in a deeply erotic realignment of ourselves, as we exorcise much of the expectation and angst of living in a racially stratified and heteronormative country. The act of a white man throating a black man's cock and taking it deep in his ass and being bred is the ultimate act of sexual subversion, from a historical context, and I find it to be very empowering for both myself and the black man who's fucking me. He's reclaiming his social and sexual power, and I'm relinquishing my own to him. It makes for some incredibly powerful and erotic moments of deep connection and pleasure
When I'm dominant with black men, it's a similar but somewhat inverted dynamic. This act, while far less historically controversial, is in many ways an even more taboo act by the social standards of the modern world, and I find it can be freeing and empowering in a very different way. Similar to how it feels when I dominate black women, dominating black men is a way of refusing to be bound by the stifling socio-cultural standards of the racially stratified world we live in now; refusing to hold back my ancestral desire to sink my white cock into inviting black asses and pussies and throats the way my ancestors did simply because society expects me to feel shame and guilt at that association. Similarly, the black men (and women) who have submitted to me have shared that the act of doing what black culture and society has ingrained in them from a young age is the single most deplorable and shameful thing they can do, submitting sexually to the colonizing oppressor (especially for the men) is similarly freeing and empowering in much the way a long exhale after holding one's breath for a while can feel. Many black people harbor a deep seated sexual desire for white people for a whole host of reasons, and most people are submissive by nature regardless of the color of their skin, so being able to shake off the shame and taboo and finally give in and joyfully submit to the power of white cock can be an incredibly erotic and fulfilling experience for them and for me. By consensually replicating a sexual dynamic that our ancestors engaged in non consensually, we're taking the bite and the power out of racism in the current world, in our own personal, intimate way
