On their own terms.
There's a certain blindness that creeps in when somebody always takes ideology at face value, esp. when there's an underdog.
So the USSR was defended by many for decades who claimed to hate oppression and nationalistic chauvinism, even as it was ruthlessly oppressive and fiercely nationalistic. Action and meaning didn't matter so much as words.
The PRC has also been fiercely defended by some on DU since I've been posting. It hadn't started a war, so it was all underdog and victim--we'll leave out Vietnam, intervention in N. Korea, the occupation and annexation of Tibet (also a cause mostly for left-of-center folk), and some skirmishes with the USSR. That it was unlikely to benefit from a war was overlooked.
In both the case of the USSR and the PRC, the rulers looked after their own interests and those they thought in the best interest of their countries, in some sense. If you have ultimate power in a country it's better to be in charge of a powerful country than a weak country. Being the Chairman of the all-controlling Worker's Party of Lichtenstein wouldn't mean terribly much. The dictator of Sao Tome and Principe, not such a big wig.
Of course, it helps to keep your power base happy and your foes cringing so neither comes to pith you. The USSR had its own way. The PRC learned from the USSR's mistakes.
So the PRC has sense. They know demographics. Japan's going to falter soon. There's a huge sense of nationalism in China--some might call it supremacism, others racism, it's a high-tech composite--and a sense that they are and properly should be the honey badger of the center ("East" is far too peripheral).