Is it race? Is it homophobia? Both? Is it size insecurity? Is it all three? What I want to know is, what the fuck is the problem? I know I've experienced these types of looks and body language when I've been at a nude beach. Why is that? Why is it one single black/mixed race man threatens some white folks? Are they afraid that it's something contagious? Skin color is inherited through genes, it's not transmittable.
If it's penis envy/insecurity, get over it. As nudists, all of us already know that size doesn't matter. At least, not the size of a relaxed penis. All dicks, when erect, have the potential to deliver pleasure to the sexual partner, no matter if that person is a man or a woman. A flaccid cock may hang nicely and swing gracefully, but that's just appearances. It's no indication of sexual prowess or stamina for the male of female partner.
Is it racial prejudice or stereotype? The black man is bigger therefore he's a threat to everyone, regardless of their sex? Come on, get over yourself. As nudists on a clothing-optional beach, we've all seen penises of all shapes, sizes and colors. Just because the darker one is bigger doesn't mean a damn thing. The myth "once they've gone black, they'll never go back" is nothing more than that: a myth. I know: I've had black ones and I've had white ones. A dick is dick. The color is the least concern (at least, as a mixed race man, for me). It's what a man can do with his cock that counts. I think we all understand that.
Is it because the brother is gay and the white dude is heterosexual? That is nothing more than stupidity. If the straight is afraid for the safety of his female date, a gay man is the very least of his worries. The gay man wants another man, another penis; not a vagina. Think about that one and then get back to me. Besides, if you hate gay men that much, get your ass off a naked beach and go to a clothing beach. They're more gay men at a nude beach than you imagine. All those unclothed cocks and asses roaming around, where do you expect them to go?
I've never set foot on a nudist beach that I haven't gotten "those" looks from straight white men. And I've asked around and know that I'm not the only gay black/mixed-race man who's had this experience. Many others have undergone the same. What the hell is it?
On the other hand, maybe it's not race or homophobia at all. Perhaps the dude is threatened because the brother has more body hair (like me)? Or, it could be the white guy is closeted and secretly wants some dick? Now, that's something to consider.