Ad hominems are not always fallacious: https://en.wikipedia.org/wiki/Ad_hominem#Non-fallacious_reasoning https://en.wikipedia.org/wiki/Ad_hominem#Non-fallaciou

Ad hominems are not always fallacious: https://en.wikipedia.org/wiki/Ad_hominem#Non-fallacious_reasoning https://en.wikipedia.org/wiki/Ad_hominem#Non-fallacious_reas... Specifically, pointing out the obviously biased nature of a source calls to question the credibility of said source, even before we get to addressing the argument itself.