It was a prison AFAIK, not a concentration camp. Most countries have prisons, for better or worse.
I'm not sure about how Kuklinski got into the army, but even if he signed up willingly, if he then discovered plans for an offensive war and so forth, his obligation to humanity overrides all else. Just as any Nazi concentration camp guard can't hide behind talk of oaths and orders either. There was no excuse for exterminating camp inmates, no excuse for even harming them. Most were innocents. I'm sure you'd agree their oaths or orders were worthless too. And that's regardless of how those Nazis got their office.
I don't expect you to agree. I don't expect everyone reading the history of Poland 1918-39 to think it sounds like a barrel of laughs either, because it likely wasn't. But that doesn't mean what came post WWII was the solution. And more importantly, that supposed solution wasn't
voted in. Therefore, that Poland wasn't 'his country'. It's quite reasonable to expect the actions he took were to get things back to the Poland he could consider 'his country' (and in the process, thwart an offensive). Ultimately, it boils down to whether someone thinks communism was good or bad, when they judge Kuklinski. Talk of 'breaking oaths' is a sideshow.