OK... when you say that science supports your claim that there is no inherent difference to different races, that's inconsistent with also saying "I have not engaged with anything resembling your hypothetical because I reject the very premise it is based on". Science is about coming up with a hypothesis, thinking about what the world looks like if it's false and if it's true, and then checking the evidence to see what the world looks like. If you're not willing the think about what the world would look like if you are wrong, you're being unscientific. From where I stand, it looks like you're super committed to having this belief regardless of what the evidence is. Not that there's anything necessarily wrong with that - maybe it makes the world a better place if people do that. But that's what I'm talking about when I am guessing that you hold position a.
And no, I don't think that's Gavagai's argument. I think his argument is that your position is scary, and you keep pushing back at him that it's not scary in practice because the conditions for its scariness can never be met because everyone is equal, and then he's pushing back with examples against your claim that that could never happen. Whether or not he has real-world examples of racial differences is completely irrelevant to the (IMO) main argument, which is about morality and racism, abstract concepts.
And no, I don't think that's Gavagai's argument. I think his argument is that your position is scary, and you keep pushing back at him that it's not scary in practice because the conditions for its scariness can never be met because everyone is equal, and then he's pushing back with examples against your claim that that could never happen. Whether or not he has real-world examples of racial differences is completely irrelevant to the (IMO) main argument, which is about morality and racism, abstract concepts.