I think it's pretty clear that the folks actually doing the playtest properly and providing feedback will not be the folks that are complaining the loudest on the forums, so I don't see the correlation between the playtest and needing to have thick skin.
You've got to embrace something in order to have any hope of molding it in your image. If you approach it from the perspective of ridicule first you won't like what happens when it starts acting like you - basic parenting.
Bias and Preference notice: I've liked the concept of paladin since I started playing in 1e. I've played paladins ever since, read most of the literature around them outside of the game and took the time to read every iteration of them since Chainmail. Along with Bard and Witch it's one of my favorite classes and I've spent a lot of time developing homebrew lore around them.
1. The most important thing for the core ruleset is to allow players options for the kinds of paladins that they might want to run, not to force things on people based on lore or what was done historically.
2. The responsibility of the DM is to take part in the narrative, take the rules and create something that agrees with his or her sensibilities AND allows his or her players to have fun. Asking the publisher to do things a certain way is unnecessary and lazy.
My sensibilities tell me that the concept of paladin transcends alignment once you take it away from its Christian Europe narrative. If you're running a game that holds on to that narrative strongly then keep it the way it was. If your campaign is different do what you will.
Note that it doesn't take much meta thought to argue that the idea of lawful good powers being the only ones that can empower martial paragons is flawed. If you can have evil priests, you can have evil paladins. The important thing though is making sure that they're just as rare in the world.
Last thought. Making something rare does not mean that you make it "player rare". Characters are supposed to be special. Doesn't mean that if your group is 50% paladins that the world is more than one tenth of one percent paladins. You just have to think it through and have your world be internally consistent with what you want.