This is the country where organised marches must have police approval and follow an approved route (and most acute in London). Hardly a surprise!

London's vibe is: 'privately owned, and you're lucky to be here'

Edit: I'm British btw (and currently sat in a pub in London) in case people downvote me thinking I'm a yank lol. There are many people who dislike London and the UK who aren't yanks

In most countries in Europe organized marches and protests must be run by authorities. It's pretty normal here.

Protesting is a legal right but the authorities do have the right to restrict it for public order reasons. For example they often will insist on separate routes to keep conflicting groups apart. It makes sense too.

Its not as if things are any better in the country that boasts the most about its freedoms regarding access to supposedly public spaces: https://www.instagram.com/780_lord_of_bench

Even within London people dislike each other!

Saw many non-Arsenal fans cheering for PSG yesterday.

There are thousands of protests per year in central London. The larger ones (tens of thousands of people) are going to be disrupting public transport routes than people rely on. There's an approved route so that disruption can be managed. Nothing to do with being 'privately owned'. It also doesn't help that for a large number of people 'protesting' means travelling into London, getting drunk, and fighting.

How many protestors did the U.K. police kill in the last few years, compared to, say, a very free country… like the U.S?

edit: responding to your edit, of course many British people hate London and for many valid reasons, but your reasoning is very American. Very few British people share that American view of freedom and would describe London as “privately owned”.