Then what? People, who are reading Daily Mail, will say 'oh nooo it doesn't have the stamp'? No, doubt you care about these things if you're reading it.

And you know what? It's fine. If we don't like some things and don't see them right, doesn't mean that everyone else should. Some people like tabloids and that's alright.

We can't force people to like The Right Thing.

I absolutely agree with you. My idea is that perhaps the worst thing about a site that claims to report news but doesn't do good journalism is just that it claims to report news. I don't think people would or should stop reading sites that don't have the stamp, I just think there are ways to allow for macro-organizations without suggesting that "the way we do it is the only way, except for complete government control."

At which point, you open the door to a media cartel that decides what is and isn't worthy to write about. At which point, your stamp becomes worse than useless, it becomes a sign of 'quality' to the misinformed while really being simply a way to say it's been 'approved' by the large media companies.

What would stop Daily Mail from stealing this stamp and slapping it on their site?

Trademark law. A more significant problem is that mainstream media publications often actively dislike each others' editorial stance, so the last thing they want to do is agree on a way of mutually endorsing each others' content. The UK, for example, has one right wing broadsheet, one left wing broadsheet that repeatedly attacks allegedly sloppy journalism at the right wing broadsheet and one notionally centrist broadsheet (run by a media empire that makes a lot of money from tabloids). None of them are likely to be receptive to the idea of certifying each other as being more reliable than other news sources.