Let me first start out by disclaiming any authority on what defines something as being "punk" or not. I am highly unqualified to draw those boundaries, so your lines won't match up with the ones I'm drawing out here.
OK, now that we've got that established, what defines something as being "punk"? I'm obviously going to move beyond the definitions of punk music, as I believe it sets up more than just music, but we'll start there.
I am definitely as Punk as someone like Herny Rollins, the band Black Flag, or some of their biggest fans, like, for example, Wil Wheaton. I think we could all agree on that. If they saw me walk into a room of punk fans who've gathered together to enjoy the thing they love so much, they probably would not let me in, and I'm OK with that. I might not be comfortable in tht room either.
But then I look around at all the people I've been lucky enough to consider friends (and who consider me to be their friend), and I think I'm fairly punk (relatively speaking). They have their preferences for music, art, attitude, etc. I'm not going to be able to convince them that they abandon those things. And I doubt they'd expect me to do the same. If they did, then perhaps I need to reevaluate them as friends (again, I'm not trying to judge anyone here as being good enough, but I'd like to think I'm grown up enough to know and accept that people change as the years roll by, and I know there isn't anything I can do about it, so I'll just accept that (which, relatively speaking, may not be very punk)).
Perhaps we're look at too big of a picture at this moment, so let's narrow it down a bit, for the purposes of this exercise. There are number of bands who I think most everyone would consider to be "punk". One of the most obvious would be Green Day. And we'll lump some bands in with them, for argument's sake. For now, we'll throw Sum 41, Beastie Boys (although they embraced rap in the '90s and made a successful pivot to it from punk, they definitely embody the attitiude required to qualify as punk), blink-182, Bowling for Soup, The Dollyrots, The Donnas (sure, they were embracing '80s heavy metal towards the end of their careers as a band, but again, they had the attitude expected of a punk operation), Foo Fighters (definitely not all that punk, but again, Dave Grohl carries the swagger of a punk musical artist), Good Charlotte (definitely anti-authoritarian, at least), No Doubt (before Gwen Stefani went out on her own as a solo artist), The Offspring, and Reel Big Fish (ska is, in my opinion, an extension of the punk sound and attitude) into the category of "Punk".
All of these groups, in my opinion, are quality musicians. If you told me that any of them were playing a show, and you wanted my input to be the deciding factor on whether we would go or not, I'd be like "yeah, let's go" (though, if you're punk, you don't need my blessing to go to the show, which is the beauty of the situation here). Now, are they all punk? Well, they check enough of the boxes on my list to qualify. They passed the "Fritz" test of being punk. Sure, not everyone would agree that they are all punk, and that's OK. What might be right for you, may not be for others. We've all got standards, and I don't expect you to conform to mine, nor should you expect me to conform to yours.
Now, as compared to my other friends? I think I'm punk. Some of my friends prefer '80s hair metal. They have the attitude of "fuck you, I'm going to have a good time", and while that's commendable, they aren't as punk as I am. Others, like modern hard rock, which have a good sharp edge to them, but since they set the standard for rock and roll, that's not exactly punk. They don't go against the grain. I am alone. I am a I-I-I-island. They could try to keep up with me, but I think if I put together a playlist of the bands I thought were punk and played it on an infinite loop, I would not tire of it.
If you want to help me broaden my mind and expose me to groups that are more punk than what I listed, I'll give it a shot. I might like it. But if I don't, and you insist on me listening to it, I may reject your standards and form my own. Because what's more punk than than?
And if you have a problem with that? Then maybe you're punk as well. Welcome aboard.