Is 4chan the perfect Pirate Bay poster child to justify wider UK site-blocking?

I genuinely do not understand where how the idea of building a total surveillance police state, where all speech is monitored, can even as much as seriously be considered by an allegedly pro-democracy, pro-human rights government, much less make it into law.

Also:

Step 1: Build mass surveillance to prevent the 'bad guys' from coming into political power (its ok, we're the good guys).

Step 2: Your political opponents capitalize on your genuinely horrific overreach, and legitimize themselves in the eyes of the public as fighting against tyranny (unfortunately for you they do have a point). They promise to dismantle the system if coming to power.

Step 3: They get elected.

Step 4: They don't dismantle the system, now the people you planned to use the system against are using it against you.

Sounds brilliant, lets do this.

The UK has never been a free speech state. Remember the extremely weird era when Gerry Adams MP could not be heard on TV and had to have his voice dubbed?