There is a lot going in to the question. Aside from the question, and the re-worded question, there are a lot of tangential questions hanging off. I've tried to answer as completely as possible.
This explanation is largely political theory, and is also largely influenced by the lectures of Dr. Meredith Bacon at the University of Nebraska-Omaha, in her course on Politics of Central Eurasia, who spent significant time in Soviet and Marxist countries.
China does have elections. In those elections people vote for the party. So China can claim that their government is elected, which provides some kind of mandate to govern. To quickly answer your question - the people did vote for them, and in some not entirely inconsequential sense, did approve of their platform.
In Western democracies, we typically associate democracy with pluralism. In this vein of thought, the government recognizes the value of having multiple perspectives or opinions on a subject. People have different opinions, and they have the ability to express those opinions through political organization.
However, if you think that your organization already has all the answer then there is no reason to have pluralism. You don't require a multitude of views, because you already know what is true. If the government is entirely utilitarian, you need debate from various perspectives to find the most beneficial policy. If your ideology tells you what the right policy is in all cases, you don't require any debate at all (except debate about what your ideology means).
Democratic centralism is a concept worth knowing more about. In American (and European) democracy, people can challenge the government's decisions. We do this through petition, protest, recall elections, public criticism, and many other ways. Part of this is about pluralism - no matter what the majority decides, the minority has the freedom not to support it.
Democratic centralism is not on board with this. While an issue is being debated, legislators (or committee members, etc.) are free to have a multitude of opinions - but once the issues is decided by a majority vote, everyone is expected to uphold it.
In this case, once the government decided that something is in the best interest of the workers and peasants, everyone in the nation is expected to conform. Since the government's policies are based on the interests of the workers, not complying with policy/law means working against the workers' interests.