Sadly, most newspapers run to a political agenda : If they just reported the news factually, and did not sift through it in order to pick out features of it that represent left-wing, right-wing or any other virtual labelling system, we would not need to get into heated discussions about it all.
Since they are partisan, it seems only natural for people to read what coincides with their own world view. (After all, if you have come to the conclusion that people of one political persuasion or another are in tune with your own ideas, or regularly appear to be raving lunatics, what is the point of reading the lunacy, which just pumps up your stress hormone levels, when you can read other viewpoints that match your own thinking?)
If in doubt, try reading the news on Reuters - it's less aggravating than the moralising press.