"The word 'communism' came from the French word 'commun', which translates to 'belonging to all'. The idea, if not the word has a long history. Centuries before there were communist parties or communist countries, there were people who believed in the simple idea of sharing the ownership and use of society's wealth equally among all its members. They thought would lead to a fairer, minder society, one in which co- operation and harmony would replace competition and conflict. People would give what they could and take back what they need. "
Political and Economic Systems, Communism. By: David Downing
Communism has the idealistic outlook of everyone being equals, taking only what they need, and giving to the community. All goods are shared equally between the people, making it a classless society.
A single party has power, but the state plans and controls the economy
To the communists, anyone who disagreed with them was either misguided or motivated by selfish interests. To allow either group a say in the way society was run would obviously be harmful to society as a whole.
Because the power sits only with one party, the people who have power are more susceptible to corruption, as they were above the law. Because of this, those with power could act as they wished, without criticism, because they were the ones that gave or denied their people of human rights.