This is really unfortunate. An anti-vaxxer knows that it’s a question of science, just as a Holocaust denier knows that it’s a question of historical record (even if they lack the scientific/historical literacy to see through the counterfactual narratives they’ve bought into). There’s insurmountable conviction on both sides—but one is right and the other is not (for all practical purposes, as elusive as objective truth is).
To refuse to even consider the moral angle—I’d be tempted to call it bad faith, but I don’t get that impression from you at all. Rather, it seems to be this:
> I take a live and let live approach to the voluntary choices of others precisely because I’m not morally superior, nor do I endeavor to be.
Taken to the extreme, the live-and-let-live / agree-to-disagree philosophy exhorts us to put down difficult questions simply because they are difficult (or seem unactionable), and to simply accept the status quo for what it is. But the moral implications of your actions do not go away simply because you choose not to examine them, or because they were the default configuration presented by the time and place you were born in.
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You’re right though; I’m not qualified to pass moral judgment on anyone, and that’s not what I mean when I say it’s a moral question. Moral virtue isn’t a contest or a report card.
Am I morally superior to a 19th-century plantation owner? (Were all slaveowners equally bad?) If I were raised in his family, as part of that society, what reason do I have to believe I’d do any different? If the answer is “none”, then why do we study history? and what makes me better than that guy?
It's not within my power to change the way things are. But the willingness to consider that the way things are isn't right might be a start.