I feel like this article makes a very poor argument for what should be an easy win.
I think the uk needs much more freedom of speech, both at a legal level and culturally (I am a Brit)
But the articles arguments are weak:
Someone calling for violent disorder during a riot probably should face prosecution. The fact the US constitution might protect such speech is irrelevant.
Similarly you can make a good argument that incitement of racial (religious etc) hatred should not be protected either. If you want to critique Islam or Israel go for it. But calling all Muslims or Jews or all women or gays or whatever other group names is likely to cause arguments and disturb the peace.
The article also focuses way too much on the USAs approach. This seems to me to have failed: on one hand the us is knee deep in conspiracy theories and far right rhetoric, and on the other people self censor endlessly (or face the consequences on an arbitrary and capricious basis).
If you’re going to argue for free speech, do it based on the inherent dangers of letting any one group decide what is banned, do it on the necessity of having clear quick communication of social changes and do it on the basis of the fastest correction of error. Not “because someone wrote down congress shall pass no law” and then a long list of judge’s arbitrarily decided what that did or didn’t protect over the next 200 years.