It's a cute series of gifs. The "fear" thing is usually more about social acceptance and expectations--maybe she's afraid to agree to a date with a Black guy, worried about 'what that means' for her identity or peer standing, what Dad will think etc.. Not so much a fear that his cock will be too much. irl when you're at the point his cock is going to come out you're already too excited to be worried about 'is it too big?' When you're aroused things like that have a way of working themselves out without so much bother
But as an illustration of a larger social dynamic this is an entertaining, if slightly over the top, way of looking at the evolution of things. Once you're over the hump of not worrying about what people will think or having some kind of a snowbunny identity crisis then Black guys and BBC do become quite addicting. It just feels like the right way to roll, going forward.