Perhaps I didn't make my point clear.
Nirvana is more 'punk' than the Offspring, in the same way Napalm Death is more 'metal' than Marky Mark and the Funky Bunch.
As in Nirvana has 'punk' roots, and the Offspring was an annoying pop band. 'punk' is no more a buzzword than anything else
'punk' was really just the original term for alternative.
and even then just for rock. everything else alternative was called industrial. This was before 'alternative rock' came along which is sadly just a lable for rock that isn't ballads intended to sell to people with no souls.
You're still just splitting hairs. In the Offspring's earlier days they played fast, aggressive music with a lot of edgy lyrics and simple instrumentation (with the exception of some impressive solos). By definition they were a punk band. The fact that they stopped playing that music in favour of something else is irrelevant, it happens to most punk bands that break the mainstream. Even the Ramones sucked out loud for the latter half of their career. As did the Clash, Bad Religion, Rancid and numerous other bands that are respected in the punk community.
I still think you're wholly misguided in your statement. That bit on punk being the original term for alternative is so incredibly off the mark that it's somewhat dumbfounding.