Is it? I can think of several counterexamples right off the bat: heroin to former addicts, alcohol to alcoholics, in general all addictions. Former cultists may have some valid disparagements to say about the cult they belonged to, all the more valid for their actual experience. An abused spouse is entirely correct in disparaging the person they loved before, especially when speaking to other potential victims.
Perhaps you shouldn't disparage the act of loving itself (though still debatable in the cult and addiction examples), but never changing your mind about the object/person/group you loved in the first place is naive.
Did you... read the article? He is clearly not advocating for never changing one's mind, and neither am I. And I don't think advice has to never have counterexamples to be useful, as most people are reasonably adept at understanding that things have contexts.
The line you quoted from Pullman includes an absolute in it - 'never'. Thus it's completely valid to bring counter-examples against it when people then promote his line as 'good advice'. If he'd said something like "I generally prefer not to disparage things that I once loved, even if I now no longer do", then I doubt people would take any issue with that statement.
We are not engaging in programming here; this is more akin to poetry. That something is good general advice is not changed if there are some exceptions. Indeed, every bit of pithy general advice I can think of has important unstated exceptions and concomitant counter-examples.
It is valid to bring counter-examples as part of a discussion, and I did not say otherwise. But I don't think it's "valid" to take a sentence, go off half cocked, and take it to an absurd and erroneous conclusion that contradicts the author's plain intent. If I'm highlighting a particularly valuable part of the article, I don't think I should have to quote the whole article in a comment just to prevent somebody taking it over-literally and out of context.
And I will note that what you did in rewriting the generalized statement is exactly how most people understand apparently most absolute statements. Nobody thinks that "a stitch in time saves nine" is literally asserting a precise 9x relationship between maintenance effort and waste avoided. It can be fun to be over-literal as part of making a joke, but when it is only in the service of misunderstanding the actual point, it's just tedious and annoying.
Quick reply to point out that the saying you referenced is "a stitch in time saves nine" and not "a stitch in time always saves nine". By including never in what he said, Pullman was being unnecessarily bombastic, in my opinion, especially when there are egregious counter-examples to what he was saying such as having loved a person who did you a tremendous harm (some sort of abusive relationship) and then, following his advice, remaining silent about that harmful person because your love was 'once real'.
As a programmer, I understand why programmers are prone to tediously over-literal thinking. Sometimes I do it myself. I just don't think it's helpful here.
In the case of heroin addiction, it is never love. It is a sickly, abusive Stockholm Syndrome relationship where you may be infatuated with the drug. You may even lust for the drug. But it is never love, because the feeling diminishes faster and faster with the years, hitting lower and lower peaks, all while demanding more and more of the user. You get to the point where you’re simply injecting just to feel sane, not to even feel normal but rather tolerable.
Very mild reminder on what the forum guidelines [1] have to say about this line (and only issuing the reminder because you've used it twice in succession).
Perhaps you shouldn't disparage the act of loving itself (though still debatable in the cult and addiction examples), but never changing your mind about the object/person/group you loved in the first place is naive.