I generally agree with the OP. Except that I don't believe in Communism. Communism needs way too much overhead and is very prone to corruption. It works in dwarf fortress, but in reality, way too difficult to implement.
IMO, capitalism is sort of like feudalism with a bit of meritocracy mixed in, in that the exceptionally skilled will be able to work up the social ladder. If you're born rich, you stay rich. An idiot born into a rich family ends up doing degrees in mass communications, business, commerce, or a language, and stays in the middle class at worst. Contacts matter way more in a capitalist economy, so that middle class guy who knows a few business contacts will be able to make a lot of money with little work. Most of the socialist world views education as an indication of intelligence, and that's because it takes actual hard work and competency to get a good degree, not money.
Trickle down economy exaggerates this effect of capitalism. Heck, if you have full trickle down economy, it'd probably be the same as feudalism. You have large areas of USA that are just as poor and stuck in poverty as many of the African nations they look down on. Try and find as many slums in democratic socialist countries.
That and the income tax model in many all out capitalist countries actually hurts the upper middle class the most - that is, the professional doctors, lawyers, and engineers who keep the nation functioning. Socialism also hits them about as hard here, but the good part is that with the free/cheap education/health care, they're much happier giving back to society.
So far, socialism throughout the world works. Capitalists have a lot more money, but socialist countries tend to be much happier as a whole. And the whole point of money is to make people happy.
But yeah, no point in arguing this. People just go bleh.. obama is socialist and he made the country broke. (ignoring the fact that expenses aren't as damn high in socialist countries)