I don't know what kind of job you work. In many companies the workers frequently are asked to do something unrelated to X such as community services that salesforce.com employees have done in the news. The disabled person wants help from non-disabled person. How one can expect them to provide services to other people?
You are wrong. They are not discrimination. You need to think about the non-disabled persons too. How their wages, employment, promotion are determined? Legally they are determined by performance. To be more specific the amount or the value of the work they did. Can disabled person perform as well as non-disabled in general? Please give me your honest answer.