If you'd like to know our reasons for doing that (or anyway, my reasons), they're twofold. First, even with the rise of China and the seeming return of global multipolarity, western countries continue to dominate world affairs, militarily and economically. It's simply a matter of scale; when they act up, it's likely to effect the lives of millions of people around the world, directly or otherwise. Second, most of us are ourselves westerners, and of those I'm betting most of us are from the the US. As citizens of these places, our first responsibility is to point out our own nations' crimes, both because of their widespread influence, and because of our proximity to them.

There's also the matter of communist countries being the subject of a truly absurd amount of western propaganda. We feel the need to push back against certain narratives about the supposed crimes of communist countries because we know many of them to be exaggerated, misrepresented, and at times outright fabricated. Most of us are close students of history, some of us like myself are even academic historians, and it can be frustrating to provide reams of evidence for our claims (or more often, counter-claims) and be met with accusations of whataboutism, rather than earnest engagement. It's why so many of us are quick to assume that the pushback we get is in bad faith, because it quite often is.

But anyway, I'm getting off track. Very few of us, I find, are unwilling to acknowledge the flaws, missteps, and yes, even crimes of actually existing socialist states, when they are well evidenced. For instance, I doubt many of us would defend the deportation of the Crimean Tatars, but we're equally unwilling to accept the Holodomor as an example of deliberate ethnic genocide because the common narratives surrounding it rely on fabricated numbers, misrepresentations of Soviet state policy, and Nazi propaganda, to say nothing of their denial of professional historical consensus.

they seem to counter it by saying a western country did the same/worse, which isn't wrong but doesn't address the point?

western countries are typically higher in every respect on the HDI and yet they often have the same/worse problems as a less developed communist country. then people from said western country flock to criticize the communist country for said problems and offer only token acknowledgement of these problems in their own country. when called out on this, they reveal a superficial understanding of how the problem manifests itself in either country and withdraw to rhetorical redoubts of 'criticism is never unhelpful' and 'i also criticize my own country (but i criticize the communist one a lot more)'.

do you see how this might come across as frustrating or hypocritical?

Also whenever someone points out a one negative thing about a communist country

These accusations are frequently false or meaningless (Cuba has the most progressive family code in the world, but we can't expect it to spearhead every social issue all the time), but you might like some thoughts that I fielded on an alt account to humor a claim made by a liberal who wouldn't have been worth the effort if I couldn't repost the thread other times like now:

https://lemmygrad.ml/post/1115203?scrollToComments=true

The problem is, they're not actually arguing in good faith. They're here to call people neolibs, spam, and pick fights. It's not about ideology, it's about a group of people who only want to cause trouble.