I’m a British journalist, so here’s a reply from inside the profession.
Firstly don’t confuse the very separate issues of (1) untrue rumours/stories(libel/defamation) and (2) invasion/breach of privacy.
There are clear laws in the UK (and throughout the world, though legislation obviously varies) concerning defamation, slander and malicious falsehood. No one would dispute that it is wrong to print inaccurate and false reporting that can cause damage to any person, famous or otherwise.
The issue of privacy is more blurred. It is possible to have the profession of “actor” or “singer” for example and keep a fairly low public profile.
Being a “star” or “celebrity” is far more a matter of choice. Now it might be argued that it’s anyone’s right to star in a huge blockbuster and not be hassled, but the reason the film is huge and the paypackets are huge is because such films are funded by the spending money of the general public. The same goes for music and television stars, and sports stars. I think this gives the public desire to know about these people, and a right to have that desire fulfilled. Tom Cruise’s mansions are paid for by your weekly cinema ticket.
Their high pay recognises their fame, “box-office draw” - the fact that these people are of interest to the public. Press and media attention is obviously the flip side of the same coin.
Telephoto lenses are a major issue - where to draw the line? I consider filming anyone someone where they believe they have privacy and should expect to believe that - in a lavatory, bathroom, inside their home, inside a private club (the secret filming of Princess Diana at her gym club was despicable) - and so on.
But in any public place - in the street, in car parks, in gardens open to public view, at premieres, in restaurants, on holiday, etc etc they are fair game. Celebrities already have huge pay, why should they be afforded any more protection than the ordinary man or woman in the street?