There's tons of people from fairly modest backgrounds in the legal profession, including ones who went to elite law schools. (E.g. Lawrence, Kansas, of all places, is the hometown of not one but two prominent south asian lawyers, Kannon Shanmugam and Judge Sri Srinivasan.) That's the direct result of the LSAT democratizing the legal profession over the last couple of generations.

I suspect you're correct, though, that if Harvard closes those doors, talented people will go to the University of Iowa (my wife's alma mater) and do fine.

It isn't that anyone things that folks from Iowa, going to the nearest in-state State college, can't make it. It happens. It just probably won't, but you might be more comfortable than someone that didn't go. Just don't, say, be a public defense lawyer or be a teacher.

It is that we know that going to places like Harvard, you are much, much more likely to have a well-paying job, comparatively. Bonus points if you are rich and can do things more often with your peers. I'm not under the impression that the education is that much better (it might be, I can't assess that). The networking you definitely seems better. You are getting a foot in the door, a thing that poor families can't always get without a good dose of luck.

There is really nothing inherently bad about sitting at the back of the bus. It is more so about the discrimination. It's a matter of principle.