OnlineDM: If you ever have too much monster in your game, I'd be happy to help you reconcile them rather than having to refuse them.
I haven't refused any, nor do I intend to. As I said, we muddle through. Would I be happier as a DM if I didn't HAVE to muddle through because the racial choices available to players were more "civilized" and easier to incorporate into a "typical" campaign? Yes. But those options do exist, and I don't want to be a jerk DM and just say "no" so I make it work.
That said, there are sometimes story considerations that would make a race a non-starter. For instance, the player who was running the gnome in my War of the Burning Sky campaign recently had his gnome
turn to the dark side and join the bad guys. In creating a replacement character, he first went with a half-orc - which is a problem because pretty much all of the half-orcs that the party has encountered so far have been bad guys.
That's not to say that a half-orc couldn't fit into this particular party, but since it would be a new character joining mid-stream, it strains the bounds of plausibility that the other PCs would just accept this half-orc who drops into their midst (especially since he's a rogue). So, I asked the player if his character concept could work as a different race, and he's agreed to change it.
If he was really passionate about playing a half-orc, I would have made it work. But he was flexible, so he's changing (probably to an elf, which is fine). Give and take between players and DMs is a good thing.