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.

Mass surveillance doesn’t seem very difficult to build if you have power. If you don’t build it, it seems like step 4 hit becomes “they build it and use it against you.” That’s not to say it’s a good idea to build such a thing, but the “your enemies will use it against you” argument doesn’t make much sense to me. The only real solution to bad guys gaining power is to either prevent them from gaining power or remove them if they already have.

But that is astonishingly idealistic in the best case.

What happens is generational shifts over longer periods of time mean that draconian law or feature has more and more chances to be used by someone with bad intentions. It's the law of large numbers or murphy's law in full effect, it's not just 1 or 2 people.