Not sure about the parent comment's stance, but for me, simply because it's "whataboutism" and all it does is distract from the issue at hand.

Can anyone explain the popularity and persuasiveness of "whataboutism"?

If "To be fair, isn't this functionally equivalent to the NSA attacks on Huawei and Chinese aircraft manufacturers over the past decade" is indeed a logically valid comparison, is that not a perfectly valid rebuttal to ~scare mongering accusations of "state sponsored attacks" from China? It doesn't nullify it, but it puts it in accurate perspective, no? And should not accuracy be an important part of such conversations?

I think it is a telling commentary on the mores of the time that there is a specific, derogatory word for the act of pointing out someone's hypocrisy.

Whataboutism is using the hypocracy of B to argue that A shouldn't be held to account for its misdeads.

Constructively pointing out hypocracy is to also call for B to be held to account. Whataboutism isn't constructive; it's obstructive.

In many cases, it's even worse. Whataboutism is often used to argue that the hypocracy of B negates the complaints of third party C against A. Nobody is claiming HP or the journalists have tried to hack the Chinese government, or that HP or the journalists support the NSA's misdeads.

Whataboutism impedes progress and should be called out when encoutered.

'Whataboutism!' is a relevant response when someone brings up some unrelated problem of another country. For example, you are touring North Korea, see a broken escalator, ask the tour guide about it, and they say: 'But you are lynching Africans in America.'

When you bring up something quite related to the presented problem, that's not whataboutism.

Ah I see, this makes sense.

In my experience, it's almost always used in the latter (incorrect) sense.

In a logical discussion whataboutism is never a relevant response. If something is bad it is bad if any side does it. But hypocrisy as a fallacy don't necessarily apply when discussing geopolitical power struggles. This is because people on one side using a tactic but not the other is usually a disadvantage, so when someone accuses you of hypocrisy they're basically saying that you're trying to get me to stop, but you won't, which will give you the upper hand, so... why should I stop?

An accusation of "whataboutism" is an easy put-down if somebody disagrees with your comment, but doesn't have any counter-argument...

Pretty low-effort stuff, tbh. It's up there with "fake news!" as a credible rebuttal.

Just because one person does bad things, doesn’t excuse the other person from doing bad things, even if they are the same kind of bad thing.

That is the essential problem of whataboutist arguments