Not to be too cynical, but the Bolivians are used to being kicked around by larger countries. They know what to expect and how to respond and fight back. Assange however takes this to a new level of humiliation for them: the Bolivians have found out that they're now pawns of a western megalomaniac who before they assumed was an ally or at least a friendly. That, and at least the large imperialist powers had the courtesy to apologize. Assange doesn't even bother, saying that his role in violating Bolivian national sovereignty was for the "greater good."
It's like an out of control police force, who, operating on an anonymous tip, kicks down your door and beats you, violating your civil rights. Yes, that's bad, but it's even more humiliating when you find out that the guy who dropped the tip was supposedly a friend you had been working with, who involuntarily sacrificed you as a pawn for what he perceived as the "greater good."