You surely have your finger on the pulse of the fanbase.
This and other message boards are the canary in the coal mine of the fan base. We are the hardcore fans and we generally shape the discussion that people have about the Pelicans. You're the only person here going crazy over this, I seriously doubt that the casual fans, who are by definition casual, feel more passionately about the Rivers issue than the PT and PR do.
I think what you're experiencing is confirmation bias, you're seeing what you want to see. If there was more support behind Rivers and we didn't see here we'd definitely see it on Twitter. I scan Pelicans related tweets far more often than I care to admit and Rivers rarely comes up at all, certainly not in a Marcus Thornton 2.0 context. I just did a twitter search on Austin Rivers
and there really are not many "I'm pissed Austin isn't playing more" tweets. There are some, but most of them are a mix of "he should have stayed in school longer", "he's a bust", "Duke vs. UNC", or "He's looking good with the second unit". There certainly is a desire to see him play more by many, but hardly anyone is emotionally invested on a similar level as you. Image: http://pdmorton.com/ArmyOfOne.jpg