Reality TV is vulgar and shoddy. By creating pseudo-celebrities it contributes to the debasement of popular taste.
It is often cruel, exposing the participants to gross humiliation for our amusement. This makes it the modern equivalent of going to laugh at the lunatics in Bedlam. The present row over racism on Big Brother shows how nasty it can be.
It exploits the vulnerable, and has been condemned by the Mental Health Foundation for doing so.
Popularity should not be the ultimate test of what is permissible. Public executions used to be popular and still are in some countries.
It is nonsense to say that broadcasters shouldn't set standards or be obliged to adhere to codes of behaviour. We don't for instance allow them to promote racism or sectarianism or to incite violence. Reality TV is debasing and should be strictly controlled, if not banned altogether.