as a white man myself who has a latinx gf i could perhaps provide some perspective from the other side of the aisle.
if this is something you truly desire out of your relationship with this gymbro, then, first, i would suggest you have a frank and open discussion about boundaries. establishing boundaries and comfort zones and having that context already established and present is key for properly moving on to discussing your kink. personally, if i was just fucking some qt and she came out of nowhere with "call me slurs when we fuck" i'd be kinda weirded out. i mean i'd still do it of course (lol) but in the moment it could be a make or break moment depending on your partner.
so with boundaries, comfort zones, and limits established (and you are sure he unconditionally respects them and you likewise reciprocate), i would then move on to having a talk about fetishes and kinks and stuff like that. framing is the key here. if you start it off with talk about kinks and fetishes he would likely be more understanding of where you're coming from with this. because again, just being told you get your rocks off from being called slurs and viewing and treating you as inferior is very weird and awkward. so hopefully you will be able to have a productive conversation about kink and fetishes.
now with we are at the final point here. having first established boundaries and comfort zones, your (and perhaps his as well) interest in various kinks and fetishes you should be in the clear to bring up the idea. most men do not wish to hurt/harm/denigrate their partners, and by establishing all of what i have described beforehand, you would have pushed the thought of him actually emotionally harming you by calling you slurs. because despite what you might think, most white people do not relish in calling people slurs. most, anyway. so when you tell them all of this, it would help them understand that it's for your pleasure, and not make them feel like they are not channeling the desire to harm or disrespect you.
tl;dr build up to it, establish boundaries, don't make it weird (regardless of gender being fetishized for your race can be a turn-off)