“I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.” – United States Supreme Court Justice Potter Stewart in Jacobellis v. Ohio, 1964.
In the same way that the exclamation point in the name Panic! at the Disco precludes any further disparagement of the band, the adjectives porn and punk free their correct usage from any further explication. As Justice Stewart (literally) observed, there often exists an archetypal shorthand for concepts that at first seem too subjective to define.
The ethos themselves are anything but capricious. And they are uniquely valid descriptions of many things beyond the sub-genre of two aesthetics first described as hardcore in the 1970s, then proactively, and retroactively, applied to their influences and influence. Anyone that truly knows their meaning, however, will inherently know that Hank Williams is punk, with no further explanation, in a way that Blink-182 is not. Sonically, this doesn’t seem to make sense. It just is.
For the same inexplicable reason, The Evil Dead Part II is both porn and punk. I didn’t invent the rule. I just know it when I see it.