I'm not sure a 'joke' is what Chris Morris was aiming at, or indeed what he used as the premise for his programme - as I understand it, he was looking for 'satire' which is not quite the same thing.
Humour is supposed to make you laugh, satire is supposed to make you think, so if that was Morris' aim, he succeeded, unfortunately it is possible for the subtlety of that distinction to be lost under the sheer weight of discomfort caused by the subject matter, and the way in which is was aimed at its audience.
If Morris planned to expose the hysteria of the media, his success was assured - one Sunday paper demanding that 'Channel Filth' be taken off the air, whilst simultaneously giving eight pages of the goings-on in the 'Big Brother' house!
I didn't see the programme, but only because I happened to be out when it was shown, so unlike the Government Minister for Child Protection who also didn't see it, I feel constrained from making any further comment.