I think most people have a negative kneejerk reaction to asymmetrical pricing when they're the ones paying more. Generally for most things, the cost of delivering a product or service doesn't vary too much based on factors like local living wages, so at the end of the day, you're paying more margin than some other people are. In some cases, maybe your group is flat-out subsidizing other groups.

It does seem people's opinions on this are cultural and situational, though. Like many people do not feel particularly upset by a veteran or senior discount. But for textbooks, I think most people feel like the massive margins publishers push are already unreasonable and thus the existence of asymmetric pricing is actually evidence that the margins are larger than necessary.

Not sure, though. Most practices that involve some form of discrimination are bound to be controversial in some way. (Even describing them using the term 'discrimination' is sometimes controversial due to the connotations that the word carries, but alas.)

Some people will even go out of their way to abuse a pricing scheme to get things for far cheaper. See cdkeys selling Xbox live cards from Argentina, for example

No, we hate that publishers make money out of other people's work.