To be honest, I don't drive myself crazy over scalpers. They exist and they're not going anywhere. I'm certainly not going to go out of my way to help them, but it's kind of a waste of energy to get so paranoid or angry about them like some people do. And I would never go so far as to ask anyone to "prove" they're a collector, this is a doll forum not a police state.
But I totally agree with your point--- because I too have seen people, not necessarily here but on Facebook sometimes, who are very vocal against scalpers, practically to the point of calling for a witch hunt, who then turn right around themselves and try to sell their dolls at the same going rate as or even higher than eBay — and no one ever says anything about it. I often wonder, am I really the only person noticing this? And this sort of thing will occur directly after a release with new dolls too, so it's not always someone selling off their collection. Sometimes the dolls are sold at retail but just as often it's at an increased price. It all seems a bit hypocritical to me. There seems to be a very fine line between 'scalper' and 'collectors who resell,' and I can't figure out how people arbitrarily decide who is who.
On the other hand, if there weren't any resellers no one would be able to get past releases they missed. So we also have to look at ourselves--for all the complaining we do about scalpers, we are complicit if we buy from them. Scalpers will continue to sell as long as collectors buy from them, so if you purchase a doll from a reseller above the retail price then aren't you contributing to the problem and just as responsible? But people aren't going to stop buying dolls secondhand -- people want what they want (and I include myself in this) so all the grandstanding and "principles" go right out the window. And I also have to mention --- having talked to other collectors, nearly all of them have let it slip that they have resold a doll at some point for some reason or another, and I wouldn't be surprised if reselling by actual collectors happens more frequently than by pure scalpers.
Also, people do buy doubles, sometimes to have one to debox or trade or because more than one person in the family collects, and as long as they are following Disney's rules of one per person, two per household, I am personally fine with that (with the exception of something like the Wedding Doll with an extremely low LE number) because they are still keeping to Disney's policy. It's the people that try to circumvent the rules and go over that amount with 3 or 4 or 5 or more or people who really have no interest in these dolls at all and just buy to sell off immediately for a quick profit that I don't like, because at that point, I'm sorry, but you're just being a pig. Still I don't let myself get terribly stressed over it, because it really is pointless to do so. There are so many people reselling right now that eventually most of them will just give it up because they won't be able to make any money with it. Just look at the past releases -- some of these I've seen for retail or slightly below retail which means resellers are losing money due to fees and such.