alt Hacker NewsConsidering the degree of "hate speech" a Tweet would have to contain to land someone in jail includes direct incitements of violence, I'm scared to ask what sort of opinion you'd like to share that you feel you legally cannot.
The claim that you get thrown in jail in London "just for sharing your opinion" is a myth, unless your opinion is, "round up everyone of race X, put them in a hotel, and burn the hotel down."
the amount of people arrested for online activity in England is not the best example to use if you're arguing that such events are rare.
otherwise, your incredulity to such a belief is why the far-right continues to gain a constituency in Europe and elsewhere. so instead of dismissing the concern, which fuels the far-right, you could just acknowledge it is a real thing people are experiencing, and that it doesn't help a liberal free society to criminalize thoughts that are unsavory to the political elite.