British spies lied about getting super-censorship powers over Youtube

The difference is that an individual can choose to ignore Government guidance. If Government disapproves of porn, tough: I can decline the filter. If the Government arbitrarily removes/blocks YouTube videos, the Government’s will is imposed without a choice.

[Yes, I know there are ways around YouTube national blocks, but if one doesn’t get to know what’s been blocked, one won’t know to look for it elsewhere.]

The difference is that, say, owning one’s own home isn’t presented as the sole option, with the Government silently, unaccountably, removing any information about the alternative.
Personally, I don’t drink alcohol, but I wouldn’t support an initiative to hide off-licences.

I’m not entirely sure I understand your point. They CAN ban terrorist videos on YouTube, and I have no objection to that.
If a video is classified as ‘terrorist’, in a way that clearly breaches the law, then I accept it should be banned. If a video is merely vaguely ‘extremist’, in a way that doesn’t breach laws about promoting terrorism, it may be distasteful, but is entirely legitimate to distribute and watch.