A great way to tell if they mean "anti-imperialist" as "against the conquering and subjugating of other groups" or instead just "in favor of anyone that declares themselves to be against the United States and Western Europe."
Most of China's alleged propaganda is just uncomfortable truths for Americans, like that our system is responsible for more death than almost all others combined since World War 2.
Imperial Japan rather famously fought against the United States and various Western European colonial powers. Had you lived back during the second world war era, would you have viewed them favorably?
But to be clear, the conflict between America and Japan was a clash between two expanding empires. We didn't fight Japan because of an outpouring of empathy for the Koreans and Chinese.
Similar can be said of a number of our enemies today though, especially Russia. This isn't to say that we support the Ukrainians purely based on empathy or that the US isn't still an exploitative power, but just deciding that anyone that doesn't like the west must be good will inevitably lead one to bad conclusions, because no country does literally everything wrong, and because oftentimes, the enemy of your enemy is just another enemy who's interests happen to be misaligned with the first one.
just deciding that anyone that doesn’t like the west must be good
Assuming you're talking about the average tankie, this isn't the position they hold. Their argument is "America is the greater evil, therefore supporting America's enemies is the lesser evil, even if those enemies aren't good themselves." Russia is about as rabidly anticommunist as America is these days, but most communists around the world support Russia against America because America is very clearly the greater evil. The whole conflict in Ukraine wouldn't have started in the first place if western powers didn't back a color revolution to replace the Russian-leaning president of Ukraine with a Europe-leaning-and-also-fascist one.