I think DMs in this position need to ask themselves if their hatred of a particular character option outweighs their love of the game. If so, please help me understand.
Well, the obvious explanation is that content dictates identity. If the inclusion of a particular character option makes it a different game, then it's not a matter of outweighing anything. It could just be a new game that you don't love.
In your mind, there is no such thing as setting exclusivity, and that's fine. But it is only one perspective.
....let me take a step back for a sec.
Certainly. As long as you take no other move actions this round, it does not provoke an attack of opportunity.
This doesn't sound to me like hatred of the kender per se. It sounds more like a hatred of a certain kind of jerk player who uses kender (or Chaotic Neutral or paladins or whatever) as an excuse to be a jerk to the rest of the people at the table.
This might be the issue for some, but it is not at all what it's about for me. I'll put up a straw man: for me, D&D will always be some combination of humans, elves, dwarves, and halflings, trained as fighters, clerics, rogues, and mages, exploring the unknown, beating down the barbaric primitives who call it home, and taking the loot they have amassed that in retrospect they really should have used against us in combat. It's not that everything outside that paradigm is "NOT D&D," necessarily, but the further you get from that Platonic ideal of D&D the greater the risk that you will trigger my "What's going on? What game is this? Where are my pants?" reflex.
The warforged are a huge part of why I never adopted Eberron, despite having the occasional ancient robot show up in my homebrew setting. The key difference is that the occasional ancient robot does not a character race make. Wizards said, "robot characters are Eberron," and I replied, "then Eberron is not D&D." We went our separate ways.
If I'm running D&D, and I am forced by circumstances to allow a player to play a warforged, suddenly we are not playing the game I want to play anymore. It's no different than the effect that me telling a player that he cannot play a warforged has on that player. When you're dungeon mastering, the world is your character. I don't force backstory onto my players' characters; why should they be allowed to force backstory onto mine?
The fact is that where a rule appears in the published material has a dramatic effect on players' sense of entitlement to the execution of that rule -- and this is by no means unreasonable! The essence of my argument is really that it is unfair to /players/ to incorporate things in their "core" books that many dungeon masters will prevent them from using. "Core" should represent the barest minimum -- the broadest possible appeal.
As an aside, I don't mind kender specifically; I didn't mind them in AD&D2 Dragonlance, I didn't mind them as a core race in D&D3 (that's right, I went there), and I don't mind them now. They're just a halfling subrace in the same way half-orcs are a human subrace. Warforged are a different story. Warforged require substantial explanation.