I have been going to WDW since I was 5. Even though I loved the ride, I would always feel bad when we got to that scene. Ironically, not because the women were being sold, although as a adult I find that objectionable. Even as a young girl, I looked more like the overweight woman in blue than the redhead. I got to watch a scene with men who didn't want her. She wasn't worth anything to them because she wasn't beautiful. And I was like her. I wanted to be the redhead so that I would be wanted as much as she was. That's what's so sick about that scene for me. I wanted to be the one they wanted to abuse, because otherwise I was worthless. This is not a static history lesson. It teaches girls how to feel about themselves. It teaches boys that it's ok to judge women based on their appearance and their sexual use.
I too always felt uncomfortable with this scene - for some of the same reasons you point out, and also for the fact that selling people was being portrayed as something jokey. This was long before the #metoo movement. Believe me, I happen to think that in many cases we have gotten pretty carried away with political correctness, but I think there is a difference between PC and being in poor taste, and this scene to me was always just inappropriate. I know all people don't see it that way but that has been my view of it since my first visit several years ago.