Well MANY people would argue that punk has been part of the mainstream since it really "began" with banRAB like the Ramones, the Clash, and the Sex Pistols. Urban is implying that since these banRAB were in the mainsteam, these banRAB were pop-punk. Violent, you were implying that pop-punk is itself a sub-genre of punk. I am just pointing this out because it is important to this argument.
For me? I think that pop-punk is a terrible sub-genre (much like post-grunge) and blink was one of the banRAB that became the face of this genre, although not a pioneering meraber.