> it was already very well accepted that you shouldn’t throw white people in jail for crimes they didn’t commit.

I can agree in general, but the case in To Kill a Mockingbird is a little more complex than that. Tom Robinson actually committed the offense of having sex with a girl whose father didn't approve of him. This was shoehorned into the legal system by accusing him of the crime of "rape". This approach is quite current today under the name "statutory rape", and is applied in a race-blind manner.

So it's plausible that if Tom Robinson had been a comparably undesirable white, something very similar would have happened. A lot of things that did happen were specific to him being black, but the very basic framework of the case wasn't.