seems to me like you are changing the goalposts here, catmilk. you stuffed up, making a valid point in a coarse way ABOUT ANOTHER PROGRAMME. if i went onto the Britain's Got Talent thread and complained that my fave contestant on The Apprentice had been chucked out, i'd just have to face the fact that i'd be On The Wrong Thread, not moaning about how everyone is too stupid to understand me.
the fact is that BTBD (and what a milquetoast title that is, btw, could hardly be less 'roll up, roll up') gives a really good insight into day-to-day life with a disabled child in the family, and as the parent of two (afaik) NT kids it IS rather humbling and perspective-shifting to watch a programme of this quality and integrity. And it HAS to be quality, don't you see, or the parents would back out and the project would fail.
Regarding the child's ability to give permission, since you mention it now - that's a fairly interesting point and one that i think the show will increasingly answer. some of those parents are making life and death decisions on a weekly basis, perhaps they have reasoned that their children will benefit more from the attention that a programme such as this will bring (would you want to be a neighbour/school child causing trouble for them? a doctor being shite and snippy on camera?)
however, in the second show, which i have already watched, it is becoming apparent that the children are making their voices heard wrt their treatment and tolerance levels, and it may be that they will drop out. for the moment, given that most parents are still agreeing to be filmed, it seems reasonable to assume that they are pleased with the show, do not feel exploited in any way and are happy to continue.