I am an adult, and I do not trust the State's judgement on what images and ideas will harm it. The presumption should be to free speech, free thought and uncensored internet access.
There are a number of laws in existence which make it illegal to possess information (images, text, videos) obtained from the internet. The nature of modern technology, including caching, means that simply visiting the sites – intentionally or by accident – puts you in breach of the law. These are an infringement of my rights to read and think what I wish.
The exception to this is pornographic material involving children, where genuine harm is done in its creation – I could not support legalisation of that.
I would also invite Mr Clegg to consider whether our democracy is so fragile that material banned for the purposes of state security presents a genuine threat.