> the majority of people who don't have disabilities
Almost 19% of the US' population is disabled in one way or another. That's a lot of folks to discriminate against. But you're right, they're the minority, so what rights should they have to get access to publicly available services? Rip out those ramps, get rid of the parking spaces, close up the isles, and shut down those elevators.
> Netflix doesn't have to caption
Netflix won that appeal, and lost the next. Rather than take it further, they made a deal and added closed captioning. So, yes, if you offer public content, it should be available for everybody. Cost of doing business.
While this content may be nominally free, it's an advertisement for MIT and Harvard classes. As much money as these universities spend on their regular marketing materials, they can afford a few TAs to add captions to their video courses.