Because the BLACK man is the epitome of male dominance and masculinity.
Let's start by looking at his body. His body is large. His domineering size makes his presence known without him even needing to point himself out. He is muscular, as a result of his high levels of testosterone. This gives him the appearance of health and strength. He is then covered by his dark skin. This dark skin reminds us of his ruggedness, a feature that developed due to being exposed to the scorching sun of africa, made to withstand such an extreme condition. It also has a psychological effect on the observer. The dark skin reminds us of our dark, deep desires that emerge from our primal subconscious past.
The BLACK man's demeanor is one of alphaness. He is dominant, assertive, and can be explosively aggressive. His behaviour strikes fear into the more timid, cowardly races of man(ʷʰ*ᵀᵉ dogs)
The summit of expression of his masculinity on his body is his penis. The BLACK penis is largest of all the races. As the penis is the penultimate symbol of manhood, this alone would suffice to make the BLACK man the most masculine of men. This large penis is able fulfill the desire of the neediest of women, being able to more than fill all the recesses of the vagina. Its length ensures that when it ejaculates, the potent african seed will immediately enter the womb of the woman the BLACK man impregnates.
In total, the BLACK man expresses this masculinity in a most exemplary manner in bed. When he fucks, he unleashes the entirety of his lusts and desires upon his partner without any restraint.
All this is the reason why the BLACK man is the epitome of masculinity