You, a lefty, discover 100 marbles, all the same size and pattern.
Some are white, some are black, and some are yellow.
You, a lefty, decide that the marbles are functionally identical, with color being only a superficial difference.
Bob, who is not a lefty, takes a keen interest in the marbles and begins to experiment with them.
Bob finds that, on average, the yellow marbles roll a little bit further than the white marbles when the same force is applied, the white ones don't roll quite as far, and the black marbles a little bit less.
It must be measurement error, you, a lefty, decide. After all, they are all marbles.
But Bob, who is not a lefty, is stubborn and repeats his experiments many times, and stands by his methodology and accuracy.
Bob wants to understand what's happening here.
Eventually Bob does a detailed composition analysis on the marbles and discovers that each color has a slightly different mineral mixture. Yellow marbles are slightly more dense, and white marbles slightly less, while the black ones are lacking the minerals found in the other two.
Bob thinks this probably explains the experimental differences.
You, a lefty, accuse Bob of racism.