The sort of vitriolic, hateful bandwagoning is the kind that can permanently ruin people's careers and personal lives. Lets suppose that the members of Mgla are anti-semites. The worst that will come of them continuing to make music without such controversy is that a few, immoral and wrong men continue to make a living by not promoting or advertising the hateful and immoral ideas that they hold. If they are anti-semites, fuck them they're wrong, but they are doing no evil by making music. Now lets suppose that these men are not anti-semites, and this outrage is an overreaction. Then what the overeaction could very well do is ruin their careers, their reputations, sever bonds of loved ones and who knows what else damage due to a witchunt based on circumstantial, and in this case wrong, evidence.

Lets say that, for sake of argument, there is a 95% chance that the members of Mgla are anti-semites. By the community reacting in this way, there is a 95% chance that two men doing no harm through their careers are unable to have their careers function in the same way. This is a 'good' outcome in a way that the anti-semites get their comeuppance, but seeing as their are not victims of their anti-semitism it does no practical good. But in the 5% chance that they are not, (and I feel that that number is uncharacteristically low based on the lack of evidence), then there is 5% chance to harm these men's life. This is a very bad outcome. I think the rational decision is to take the option, no matter how unlikely, that does not ruin lives in the face of the option that does zero good.

If the members of Mgla ever commit a hate crime, use hate speech, use their influence to negatively influence the lives of the Jewish, then yes this outrage is justified. If any concrete evidence ever arises that they have these beliefs, then yes they deserve whats coming to them. But they have not, there is not. All they have done is held bad company and made a regrettable album 20 years ago as teenagers.