I think party politics encourages intellectual laze, basically being part of the group makes you want to be on board with the party platform, as opposed to having a more complex political makeup.
And the same goes for art criticism, I think it's a bit strange to have a second hand opinion. Though it is still interesting to see someone's well thought through take on something to look for details you didn't notice. Mind you, I think that's where the whole "ruined" thing comes from. Ignorance can be bliss, unless you are ignorant of an oncoming train.