@amici Marxist materialism didn't make it immune to bias. Quite the opposite. Marx believed very strongly (as most narcissist people do) that he discovered unique and absolute laws of history and economy. When observation didn't match the "laws", instead of modifying them he adapted his "analytical apparatus" to bend the reality around the laws, and then argued the "bourgeois science" is wrong, thus undermining the very basic assumptions behind scientific approach.