"I'm just a little puzzled as to why, for so long, this term has been used in such a derogatory way, about people who actually DO give a damn about things."

Maybe because a lot of the articles printed by the Daily Mail seem to stir up a particular type of political response. And the people who take up that gauntlet can be very reactionary and right-wing in their responses, which is not really surprising considering the paper's place on the political spectrum. To you, they may "give a damn". But the sorts of campaigns whipped up by the Daily Mail are often ill-considered, knee-jerk reactions and based on little more than paranoia. IMHO, of course.

I realise that not everyone who reads the Daily Mail is a fascist - my ex-in-laws were Daily Mail readers, and while they were and are lovely people, I do know that the constant barrage of negative stories about immigrants, asylum-seekers, racial tension etc have had a distorting effect on their political outlook.

All 30,000 people who contacted the BBC may not have been Daily Mail readers, but it's the paper which originally broke the story and encouraged people to contact the BBC.

FWIW, I think The Sun is the highest-selling UK newspaper.