-We are governed by a capitalism which has a right to destroy our planet, seems to be doing so with unbridled CO2 emissions, and this is unsustainable & illegitimate.
-The public should have the right to stop this capitalism, as its actions -committed by a minority, privileged elites- concern all of humanity.
Capitalism works to dethrone, and expel democracy:
On a spaceship, it is evidently criminal to exclude certain members from air, food and water rations, and the consequences of monopolizing even one of these goods - or having an unequal distribution in any way - are obvious. If the team even had a functioning democracy, we all know how any vote would go if one member could deny others any amount of these goods.
Voting with "dollars" or "feet" (walking away) is not democratic because it involves cost mechanisms which defeat free choice. Money is limited, and its magnitude acts as a barrier to acquisition of food, shelter, and other items which will consistently supersede our interest in having a free choice (especially as a lone voice) in a democratic system.
Time is also valuable; investing hours, months, or years in systems means that rational human beings will always have a threshold for when they will assert the right to walk away. Human beings are naturally not inclined to walk away (or to seek out problems with their economic lives - which is why meat production is allowed to literally disgust human beings at every stage, and yet remains so disgusting, for a product for which disgust would normally be a major marketing problem.
People don't want to know who suffers for their goods. Would you be eager to learn that you are paying for crimes - of any sort - when you buy certain products?
Chumbawamba - Sewing Up Crap
Capitalism defeats rational, deliberative human choosing mechanisms, especially inside democratic bodies. It is not based on the democratic influence of affected members of society, but on the power brokerage of a privileged elite. This privileged elite may specifically benefit from actions which harm the rest of society - such as increasing CO2 emissions. This also makes it an unsustainable system. Capitalism has no legitimacy as far as social consent and input, and is destabilizing at least socially and environmentally. In literally every instance, the socialist model breeds legitimacy, stability, and sustainability where capitalism breeds the opposite: capitalism means public decisions made without consent by minority cliques, instability, and industrial activities which threaten human life. The principles arising from socialism are also the principles which ensure a robustly democratic society. The socialist difference is simple: make the market also democratic, rather than dictatorial.
In a socialist system, the public, not the minority/capitalists, controls that which hangs over the public's head. It is rather obvious, too, that the public should indeed have the power to defend itself against acts of private power.
Socialism means the democratization of economic life. That is not without pluralism - you don't get to democratically decide that no-one can have chocolate; like in standard democratic/legal and civil standards, you only get to legislate that which impacts outside the individual actor. Socialism is legitimized by including all stakeholders - those affected - in influence over that which affects them.
Capitalism is a way to undemocratically distribute power. To enact a market, with legal precedent, to give away so much power that even Global Warming - possibly the literal destruction of the human race and other life forms - is a legally protected aspiration of private industry. Even when that industry is a minority among industries. That level of legal right to exterminate life is quite unprecedented. The only legitimate and stable alternative to dictatorial, capitalist economic life, is democratic, socialist economic life.
Communism is (for most people) synonymous with this socialism, typically a form of the idea which is much more radically manifested. Most of the standards rely on the equal distribution of power (democracy) over industry. The extent of distinction between democracy and communism, among even the hardliners, is that in communism there is no longer a state apparatus to have a formal democratic system.
Communism is stateless and that is why communists don't like to use the term "state" to describe what they advocate. It is the ideal, humans can probably achieve, that makes a socialist way of life informal (and thereby social conventions are less onerous or inefficient). This is likely possible because people can and do act in concert with one another - to make stable social systems - by default.
Socialism is in some ways a point of concession toward communism. That could be because of the transitional phase of time. That could be because it is plausible to institute progressive taxation and worker possession of factories, but not the full reappropriation of past human production to solve shared problems (such as environmental catastrophe) before it becomes a toy for privileged individuals.
The communist is an archetype of the crazed, dictatorial statist - the very thing the capitalist aspires to be. Plainly, communist, not capitalist standards are at the core of democratic principles. The lack of public consent, lack of legitimacy by social approval, is the capitalist model.
The communist standard of power is simply put the democratization of power systems - necessary at a time when even our environment, and continued existence, may be immolated as a "tragedy of the commons" by abuses from industry.
Pluralism means "Society works for everyone":
In all ways, systems should be redesigned to better serve all members. Human social systems can and should be based on good-faith interactions with humans that lend themselves to improved outcomes. Deleterious effects which outcast members of society truly squander human potential, are less legitimate as they do not serve society broadly and in a pluralist manner.
Systems which doom members to homelessness or imprisonment represent squandered possibilities. They could instead leverage human desire to be accepted and serve them in basic, dignified ways, to stabilize their time in our society.
There is a possibility for society to be stable, sustainable and legitimate. In every possible case, the means of production are leveraged, and under the thumb, of all of the public. This also literally means that democracy defeats and expels capitalism as the model of design of society. Dictatorships(capitalists) are replaced by democracy(the public). That is plausible, and likely, because the mass of humans are able to act collectively.
1. Adam Smith - Wealth of Nations