American IQ scores have rapidly dropped, proving the 'Reverse Flynn effect'

I mean, it's still precisely a fallacy. Just because someone made a stupid or wrong argument 20 times in a row doesn't make it logically follow that the 21st is also wrong, without examining that argument itself.

Of course, it's a useful heuristic to determine if it's worth your time to examine it.

Just a meta note, this is why fallacies are limited. Just because something is a logical fallacy, meaning it does not lead to a disproof in a deductive reasoning sense, doesn't mean people often use arguments that could be considered fallacious to disregard arguments all the time as instead they use good heuristics.

Deductive reasoning is valuable but only applicable in a small number of real world arguments, as with math it generally has to do with determining consequences of an assumption. Heuristics and just plain inductive reasoning is generally what arguments are really about most of the time.

Science, properly done, is about convincingly explaining how your propositions might be true, usually deferring to a branch of mathematics.

Being known for making leaps in this process and draw unwarranted conclusions is sufficient to make one suspicious and warrant extra scrutiny on other conclusions.

There are many ways to fail in scientific process, if even by pure luck. And yet more by systematic error.

Ad-hominem and appeal to authority is an annoying tactic one has to successfully defeat. Declaration of "it's a fallacy" is worthless at doing so. What you need to do is still to present your arguments in a solid way, at which the blog post failed anyway.

The ad-hominem does not apply to classification - you can make a classification mistake, but ad-hominem is not about that. It's about attacking the author's directly, and an argument that a source is unreliable because statistical claim is not of this nature as it relies on proposition to be shown true or false. Ad-hominem relies on a true but irrelevant fact. The argument above relies on a relevant proposition.

So by mentioning ad-hominem (which is quite specific) in a wrong context, you have made an argument from fallacy fallacy and additionally a pure mistake.

The one you might have wanted is Fundamental Attribution Error also known as correspondence bias, since the talk is about classes of authors and their trustworthiness based on publication medium. Even then, the claim on reliability of blog posts is to be shown or disproven, not offhand discarded.