I can't see acceptance of new races in the PHB as a generational thing. I'm old enough to have read pretty much the entire Lieber, Howard, Moorecock, Tolkien and Vance corpus. I'm also a classicist by training and vocation (I teach Latin and Mythology).
Most of my group is as old as I am (with two who are a little older). The general consensus seems to be in agreement with my own opinions.
I really like the new races in the PHB. I probably won't play one (almost all of my characters are human, but I have an idea for a tiefling), but I've enjoyed working them into my upcoming 4e campaign.
I see very little similarity between D&D elves and the Lojosalfar, or between dwarves and dvergar. Don't even get me started on gnomes and halflings.
It would seem to me that a lot of folks get upset because 4e will include races that weren't present in Tolkien. Most of the other authors of classic fantasy hardly included non-humans at all.
For decades D&D has been shoved into a tiny little Tolkien shaped box. I'm so glad that 4e will be finally be allowed to crawl a few inches out of the box. If PHB1 included rules for fauns, centaurs, changelings, shifters, warforged, goblins, hobgoblins, lizardfolk, etc..., we could say that the game had finally broken out of its constraints and become an actual fantasy game (instead of very poor Tolkien simulator).
Oh well. It's a step in the right direction.
I wrote the post. Of course it's my opinion.