In order to take advantage of someone you must other him or her. This is a required part of hierachical structures like, for instance, capitalism. We don't take advantage of people we identify strongly with. For people to play their part in a system of control we must look for and create reasons to separate "us" and "them". This othering of people allows to do nasty things to each other without the cognitive dissonance that would occur if we did these things to people that we thought were much more like us than not like us. We cannot treat people like machines when we think of them as people just like us.
Disability is a very important othering to undo. It's from disability that we take our most fundamental (and incorrect) measures of man [sic]. Our physicial prowess and mental capacity are accorded greater value than something like honesty, loyalty, humanity, etc. If these latter qualities were more highly regarded then we would have to stop othering people with disabilities. And then we would have to stop oppressing them.