Well yeah if you want things in life you need to offer something in return, obviously the doctor isn't a slave at your command to work for you for free. But you need not be employed to employ his services, merely need to compensate him for his employment in your service.
Your options are to offer the doctor something, ask for charity, or use violence (either yourself or through the state) to force someone to give you what you want.
Obviously I am not going to advocate for violence.
One may be that in their particular case they can get away with it, it works, and they can blame the victim as not having a right to keep what they took in the first place.
We can go full postmodern - what gives anyone a right to anything in the first place anyway? In the end, isn't it whoever has the most capacity for violence who has the "right"?
You could consider that, but focusing on the violent option (curiously so far to the exclusion of everything else) and then beyond that focusing on rights based on capacity for violence may not be the path that comes out with the most benefit to the disabled.
That hardly disconnects it from being employed, unless you are fortunate enough to have savings/inheritance/etc to fall back on.