They are equated under the principle of injustice anywhere is a threat to justice everywhere. You could make the argument that Black people have suffered more at the hands of society, but the injustice of both are in the same class: prejudice.

>You could make the argument that Black people have suffered more at the hands of society, but the injustice of both are in the same class: prejudice.

Again, this is exactly what I am saying.

I am also saying that you go further, and engage in an intellectual slight-of-hand. This happens precisely when you say "there's really no difference [...]".

Yes there is. There are several, important differences that render irrelevant their belonging to the same category. Abraham Lincoln and Pol Pot both belong to the category of "heads of state", but it is laughably incorrect to claim that there are no differences between them. So too with your example.

What you are failing to understand that there can be "no difference" between doing things, yet there is a large difference when one of them is done a lot more and more intensely than the other.

That's the difference between anti-short and anti-Black, not the anti-ness itself.

"There's no difference between anti-shortness and anti-Blackness, except the intensity and commonality" is certainly a statement, its I guess correct in the tautological sense that "X and Y are not different if you exclude all the differences between them", but it's also not a useful statement at that point.

I'd ask in what way the point you're trying to make is useful, either analytically or rhetorically. I don't see how it is offhand.

They are not equivalent and I disagree with the OP's example. Racism is significantly worse. That doesn't mean heightism/lookism is not an injustice worth examining and discussing however