On which grounds do metal elitists condemn Avenged Sevenfold more for plagiarism than Led Zeppelin?

I’m not even sure which school of ethics could justify the belief of metal elitists that Avenged Sevenfold “copying” from white (or mostly white) rock/metal bands is somehow more morally reprehensible than Led Zeppelin outrightly exploiting black blues artists.

The two major schools of ethics I subscribe to - the “golden rule” and the “harm principle” - are what I use to support my belief that Led Zeppelin is *far* more guilty of plagiarism than Avenged Sevenfold is. Just ask Howlin’ Wolf and Willie Dixon.