You could argue that people living on minimum wage and effectively only being able to do the things that society makes cheap enough for them is degrading too. Ultimately what I'm saying is that as humans/ponies we often prefer the thing we choose over the thing we'd rather not. That is to say that most of us would prefer to be full and have a roof over our heads than freedom "at any cost". It may not have been her choice to be enslaved, but whether to just put up with it and be fairly comfortable (by standards of the Equestrian Wasteland) or to fight every step of the way/try to escape and probably be beaten/etc over it and maybe end up dead is a choice. The zebra there is probably arguing that the former is preferable. Freedom may be theoretically better, but most would choose relative comfort over freedom with substantial discomfort and regular suffering. The evil you know over the evil you don't as it were. Assuming she escape, she might just be captured by some raiders who'd kill/eat/use her however they wanted without any benefits. It really sucks to be a mare alone in the wasteland... especially if you aren't some kind of super soldier, a one-mare killing machine, walking timebomb, etc. Straight up dead might be the luckiest way to go.