If I had more time, I would read the Daily Mail and any other paper I could get my hands on. It's very difficult to have an opinion of any substance or value, if you don't familiarise yourself with the different elements in the media and the way in which the available facts are interpreted by different organs, IMO. I have made myself watch films which I knew I would hate, in order to be able to join in debate about them. I even forced myself to read a Martin Amis novel for the same reason.
So IMO it's a bit facile to say "You read this paper, so you are X and Y". Although I am guilty of making assumptions about people who write for particular papers, and I've been proved wrong in that a few times as well.
There are plenty of ignorant and crude assumptions made about "lefties" and "guardianistas" on MN at the moment as well, which don't seem to be attracting the same level of righteous indignation, which is interesting.
I personally think it makes more sense to make assumptions about people's political views on the basis of their voting habits than their choice of newspaper. But that's a different thread