>>> Yet here the author claims that believing something can be morally wrong even if it is a true belief? No, the author is claiming that belief in a statement

>>> Yet here the author claims that believing something can be morally wrong even if it is a true belief? No, the author is claiming that belief in a statement can be morally wrong in the absence of definitive proof or disproof of that statement. In other words, morality can tell us how to treat a statement whose truth or falsehood we don't yet know. The author is saying "if we didn't know whether older programmers are better or worse than younger programmers, it would be morally wrong to discriminate against them; however, new research says that prejudice isn't just morally wrong, it's also mistaken." But you're right, the idea of using Stack Overflow scores as a proxy for programming skill seems a bit sloppy. On the other hand, do you have any evidence for "the average quality of all programmers of a given age decreases above some age"? I'm not convinced that promotion out of being a programmer is that strongly correlated with programming ability. But I may be biased, as an older programmer who's tried (with gradually decreasing success) to avoid all managerial responsibility.