Yes, but they accept federal and state money, just like when the UC's accepted federal money and decided to submit on the issue of military recruiters on campus, because getting federal funds is voluntary and to the nearly arbitrary discretion of the executive branch.
However, I do think that there should be more mechanism than the purse to persuade institutions to make material accessible to disabled populations -- but for major institutions only, since I'm not sure smaller organizations can cope with the burden. Perhaps organizations above some revenue?
Doesn't that parenthetical comment destroy the rest of the [small sub-]argument: because you paid someone for doing research doesn't mean that if they decide to make something else free to access that you have a right to make further demands of them.
If central government just gave them a stipend and didn't specify the projects it was to be used on then the argument you're supporting would perhaps have some mileage; but it's payment for a specific service. If the schools aren't making their research centres accessible or are unnecessarily excluding disabled people [from research related tasks/benefits/etc.] then, yes, this argument would be valid.
However, I do think that there should be more mechanism than the purse to persuade institutions to make material accessible to disabled populations -- but for major institutions only, since I'm not sure smaller organizations can cope with the burden. Perhaps organizations above some revenue?