Most people don't question the contradictory nature of democracy and capitalism, even though, in hindsight, it seems relatively obvious. Democracy is the largely political idea that every member of a society deserves power over that society, and is depicted as being fair. Capitalism is the largely economic idea that the most successful of a society deserve power over that society, and is also depicted as being fair. In mainstream democratic as well as capitalist thought, these two ideas are both fair and compatible. However, while they may supposedly both be fair, there are many different kinds of fairness.
While democracy is pretty well-understood, we should first go into some depth about capitalism. Capitalism bases itself on the private ownership of the means of production. This differs from prior systems like feudalism, which put the means of production into the hands of the state or a similar entity with mainly political power. The “fairness” of capitalism arises from the belief that it gives everyone the opportunity to succeed. According to capitalists, anyone can make some money as the proletariat, use it to become bourgeoisie by purchasing the means of production, hire proletariats to work via it, use the compounding profits to expand by purchasing more means of production and hiring more proletariats, and maximize economic power. This may very well be a fair distribution of power, but it certainly isn't a democratic one. To exemplify this, let's imagine if capitalism's distribution of economic power was applied to the distribution of political power.
In this world we're imagining, there is no government nor any other preexisting political entity. Instead, everyone is trying to become that entity and they each have the opportunity to succeed, though whether they make use of that opportunity is up to them. Let's say that I'm ambitious and want to use the rules (or lack of them) of this political system so that I can accrue as much political power as possible. I start by acquiring resources of my own, either by collecting them myself or stealing them from others. Once I have enough, I hire some less ambitious people to become members of my posse, allowing me to collect and/or steal even more resources than before. My posse, as well as my wealth, grows in size until both are big enough to found or capture a settlement. This provides me with even more people who can acquire more resources for me and increase the size of my posse — now army — so that I can take more resources, people, and settlements. I take a cut from each of my subjects and funnel it into projects and initiatives that increase their effectiveness at acquiring resources for me. More settlements come under my control, and my power compounds as they all, willingly or otherwise, swear fealty to me. I hire people to managing the minutiae of government for me, paying them well to maintain their loyalty, while I focus on the big picture issues related to me increasing or protecting my power. I make alliances, wage wars, stage coups, arrange marriages, and a whole lot of other things until I reach the top, having achieved the apex of political power completely fairly.
From the capitalist perspective, those last words are completely accurate. My hypothetical rise to political power completely mirrors how capitalism encourages people to rise to economic power. Logically, every capitalist should want the same thing to happen in real life. But they (ignoring AnCaps) don't. Why don't they support the political system which led to the dominance of High Overfiend BadassPlaya2517? Because it created a tyrannical dictator. It created a tyrannical dictator because it applied the logic of capitalism to politics. By capitalist logic, I did nothing unbecoming of a capitalist. I used my inborn traits, such as charisma, intelligence, or deception, as well as the labor of those I paid to labor for me, to make it to the top. I was the most successful of my society, so I deserve power over it; right? I won fair and square. However, I also did so in an extremely undemocratic fashion.
This should be no surprise, seeing as capitalism isn't a democracy. It's a dictatorship which simply compounds economic power instead of its political counterpart. A dictator may have attained his position fairly (assuming that the phrase “fairly-appointed dictator” isn't an oxymoron), but that doesn't make him any less of a dictator. Why do we just accept this? Why do we tolerate the existence of both democratic and dictatorial distributions of power? Why do we draw an arbitrary line between one kind of power and another? Why do we cast votes for people to forward our interests in every echelon of power only to accept the absolute power that someone else has over ourselves and our production? It gets worse though. Why? Well, let's say that you still accept this world of dual power between democratic politics and dictatorial economics. Let's say that you're fine with the arbitrary line. That's okay. However, you fail to take into account the fact that I lied. There is no line. Political systems are economic as well and vice versa. There is nothing separating democracy from dictatorship and dictatorship is seeping in.
I could reference a countless amount of evidence to prove this point, but I'll use lobbying. It is legal for the bourgeoisie, dictators of capitalism, to pool their resources so that they can sponsor a potential legislator of our democratic government. This chosen individual is incentivized to vote on and present laws in ways that benefit their patrons so that they can attain funding for reelection. They do this even when they might be acting against the interests of their constituents. In essence, the dictatorial economic power of the few can and often does override the democratic political power of the many. They are literally buying political power with a portion of their economic power to control both spheres. Dictatorship is not being contained. Rather, democracy is being infected and degraded by it. Capitalism and democracy simply cannot coexist because they are inherently contradictory.
However, this detrimental nature goes both ways. Capitalism can violate democracy, but democracy can violate it back. When economic power is more equally shared, the power of the few at the top is weakened while that of the many below them is strengthened. Unions are one example of this. The very concept of collective bargaining is based on the assumption that the proletariat has or is deserving of any power over their bourgeoisie dictators. It shows a complete disrespect for the Social Darwinist justification of capitalism. We may not have won the scramble for economic power, but we demand it anyway. Democracy and capitalism may be unable to both remain, but we can decide which one does.