You give people to much credit. The reason it sells is because they want to read trash. Boring, factual news papers of the happenings of the world don't sell anymore because the Internet has killed them. You can read it anywhere at anytime. Lies and sensationalism are unique to DM (and a few others who try to copy the same model) so it stands out and people will buy it in paper form to read on the train to work. It's more like a magazine in terms of content. It'll die eventually but they'll keep adapting to maintain reader interest until they push it to far.
I don't think it will ever go too far. The masses are slowly conditioned. I remember not that long ago any form of blood or graphic content on the news, or even meal time, you were warned about graphic content. Now they show dead bodies and limbs you name it with no warning.
You get a story and such that will offend people. They'll storm twitter and the likes. It'll last for days then whatever breaks, they'll flock to the latest thing.
The media can play the public like no tomorrow. There's no accountability.
Most people have short memories.
I do however enjoy seeing journalists become ratty when incidents have occurred and they were in the wrong. How hostile they become and group up trying to defend themselves or justify it.
I'm sure 10 - 20 years from now, people will still be posting the same things you're saying now.
I'm slowly fading away from the BBC/Sky News/Newsnight as it's full of mind numbing stuff these days. Plus it's so pathetic watching giddy journalists/presenters. They'll do anything for ratings/viewers. Then preach about morals/immorally wrong. Just like the masses. That and we seem to have an ousting culture these days.
It'll never change. Same problems exist just delivered in another format.