well, i have always liked to think of punk as an aesthetic over a sound. the aesthetic being, "lets make art the way we wanna fucking make it, fuck if anyone listens to it/likes it, and fuck them if they wont release it, will do it our fucking selves". therefore, to me, black sabbath is punk, to live and shave in la is very punk, alejandro jodorowsky is the most punk ever, etc..
but im talking soundwise here. sabbath's riffs definitley played a part in punk. people get thrown off by the speed, because obviously, sabbath was slow. but im telling you, go throw any of the first 5 sabbath record on a turntable and turn the speed up, at some point itll vaguely resemble early punk or hardcore.
listen to pink reason