I think why you think “disabled” is rude is the thing to focus on (and the answer very briefly is because you, we all, were socialised to think that way).
I’ll just drop this link in too, I think intersectionality is vital, and understanding how systems of oppression stand alone and interact with each other is vital to unlearning them, and I think this is a good starting point that goes in to several: www.yorku.ca/edu/…/systems-of-oppression/