Personally, I think it's fun to play around and dial in Kurt's sound and jam for a bit. If people think that makes me a wannabe, I just don't care. After all, the sound I have for *my* music is soooooooo on the other side of the spectrum, that the mere suggestion is insane.
If these kids are just now discovering Nirvana and want to emulate his sound, then let 'em. It won't be too long before they tire of it and begin developing their own sound.