Do you think their tirades are based upon their, to me at least, universal position of perpetual victimhood? It seems to me they have the common trait of being victims and the only way they'll ever improve is for a liberal government to give them money and 'make things right'.
Whenever my Dem friends go off on their rants, I try to pin them down (and calm them down) and try to actually discuss the issues rationally. It's usually a very ineffectual attempt, because they don't want to calmly and rationally discuss issues, they want to rant.
And you're probably right. Although they all have more material possessions than me, they feel that somehow they've been wronged. Usually by the ever mysterious "them". It's as if life has cheated them out of something that is rightfully theirs.