Step in the Right Direction. Like Jim Crow Laws
This doesn't have so much to do with accessibility as it does the thought you brought up and then was provoked in another class the next day. That of racism. I wonder if it ever had anything to do with skin color. Or if it was just the society that that people with different tegument pigmentation are perceived to bring. You justify the enslavement of blacks because they're so primitive where they come from, they're not really human. Humanity carries a certain grace, even if you share the species, if you don't have that class, you don't count. And so blacks are frowned upon because of their percieved savageness, making them good for work, you know, like a cow or a horse. But they got thumbs, so you can have them pick the cotton or clean your house without as much fuss as a cow.
Get rid of slavery, those perceptions are still there. You don't want these folks running free, they'll just revert to their old ways, we'll have Africa in our backyard, that'd be horrible! It's still not really because they're black, just because they're from such a barbaric place or share ancestry with it, a few generations down. And they've only been procreating with their own kind, so the barbarism couldn't have gotten watered down. Anyway, we'd never want to lower our civilization to their level, so they won't really ever get to breed outside the circle to ever get any better. Enter reproductive and social controls stage left with the Jim Crow laws. Gotta preserve our civilization and not let those savages run amok. Still doesn't seem like it's got anything definitively to do with skin color. Just heritage and where you're from and a fear that an undesirable society there could spread here.
But I dunno, now everyone would be quick to tell me that it's always been about skin color. But we don't hate trees because they're brown. Or prefer specific trees because of bark color, as a society at least. But I don't think it's really fair to compare the Americans with Disabilities Act to Jim Crow laws because of that fear and protectionism that are there with Jim Crow but not with ADA. We're not afraid of people in wheelchairs and want to make sure they can't effectively get into our buildings. We're just too lazy to really do anything better.