About the R32 badges, hell no! You might as well get a Lamborghini emblem on your GTI. Sinful, tacky, and just plain stupid.
The "R32Killer" badge? Okay, this is a better idea (if you can, in fact, take out an R32), but still not entirely appropriate. You just don't see enough rivalry between the GTI and the R32. "CivicSiKiller", "STiKiller", or even "Smokin'Rice" would be better choices IMO.
I once saw a Dodge Neon (pre SRT-4) with a sticker on the back window, "Import Killaz" or something like that. I thought that was pretty clever until I smoked him in my stock '87 Rx-7. Now that I have my GTI, I can't wait to embarrass the dumbass with that sticker on his Cobalt.