The advocates of socialism and communism assume, on principle, that the individual belongs to the state and the state can do whatever it wants to him. This premise, being the singular operative premise of communism and socialism, makes their moral natures and actions so similar that they can be understood solely on this basis.
Contrast coercive governments with capitalist systems based upon the individual, and you will understand why communism and socialism oppose capitalism. The proponents of these coercive systems do not want the people to know that force and capitalism are opposites.
In fact, the coercive nature of communism and socialism is the reason these systems do not work; and it is the lack of coercion in capitalism that creates the abundance and prosperity normally associated with it. It is also the freedoms of capitalism that move dictators and technocrats to want to do away with it. As long as capitalism flourishes, as Marcuse averred, there is no way that communism and socialism can advance beyond it. This is because they are inferior systems relative to the individual.