However Facebook is grouping people together into groups who only receive messages that reinforce these kinds of beliefs.
It is amplifying and hardening them and making them more extreme.
Is it the cause? Of disagreement? no. Of the extreme polarization? Yes, is one of them.
An entity which has access to easy credit can throw that newly printed currency on any asset and it will balloon in value over time at an accelerating pace... No matter what the asset is. The value of the collateral will increase faster than their underlying debts; these entities can thus keep borrowing in perpetuity. They can keep it going forever, so long as banks keep loaning them more money...
Banks cannot stop loaning money to big capital holders because they know that it will lead to a catastrophic economic collapse. They are stuck in a vicious cycle wherein big corporations act like governments; constantly taking out new bigger loans to pay for the older loans... Or engaging in credit laundering through the use of shell companies.
Wealth inequality leads to inequality of opportunities which causes inconsistent experiences of the same economic system and causes polarization. One side's experience is characterized by constant struggle with repeated and almost inescapable failure (obvious glass ceilings everywhere)... The other side's experience is characterized by repeated success with little effort required and so they think that people on the other side must be extremely lazy or stupid.