In the West, we see democracy as a means of limiting the excesses of power. As Karl Popper noted, 'democracy' is not so much the answer to the question "who should rule?", as to the question "how do we prevent bad rulers ruling absolutely?". When 'democracy' is taken to imply the first answer, it is seen as the grounds of total legitimacy for the ruler. It is simply a substitute for the divine right of kings. In the second case, the ruler seen as having limited legitimacy, subject to the rule of law, of criticism, even ridicule, and of lawful challenge from other potential rulers.
When totalitarian states called themselves 'Democratic People's Republics' they were not so much lying as using the term 'democracy' in the first sense above. They were signaling that their governments had a legitimate claim to absolute power on the grounds that they were the expression of Rousseau's 'general will'. Those who clashed with the state were not seen as rebels against the ruler, but as 'enemies of the people'.
Under the leadership of the Communist Party of China [...] the Chinese people of all nationalities will continue [...] to turn China into a socialist country that is prosperous, powerful, democratic and culturally advanced.
http://www.npc.gov.cn/englishnpc/Constitution/2007-11/15/con...
Of course the literal text of the constitution is completely ignored in practice, but criticizing that doesn't automatically lack credibility.