That's not entirely true and your analogy is not comparable. Person A makes a claim that X is good and everyone should be doing it. Person A does the opposite of X. That doesn't prove one way or the other the truth of the arguments but it does call into question what the goal is with the arguments. There could be many reasons for such a discrepancy but a common one is manipulation.
As an example, if a crypo currency executive says their coin is fantastic and everyone should invest in it, but sells their entire holding does one not question the goals of such a statement? Note: this example is also not directly applicable to this article (at least I hope it isn't) but it's closer than your example was.
I will concede that it is not completely analogous. But you are talking about something else, namely the value of the intent behind a claim.
As I argued, intent has no bearing on the truth value of the claim, but it can – as you point out – be correlated with the truth value. I stand by that dismissing an argument based on intent is fallacious. You have to honestly deal with an argument – regardless of the messenger – to assess its truth value.
I don't disagree but I also don't see where that was suggested. The OP just pointed out the radical difference between what was preached and what was practiced. This could be seen as a dismissal but it could just as easily be seen as a call to action or just pointing out something amusing.
As an example, if a crypo currency executive says their coin is fantastic and everyone should invest in it, but sells their entire holding does one not question the goals of such a statement? Note: this example is also not directly applicable to this article (at least I hope it isn't) but it's closer than your example was.