I watched it, I thought it was moving and considered.
The Baddeils are obviously a very 'individual' family, their father was, even pre dementia, a bit of a character. It seems to me the sons have tried, as far as possible, to continue with their normal family dynamic which involves lots of humour and swearing!
As David said at one point, (I'm paraphrasing) he wanted people to know that dementia doesn't just mean that somebody sits, mute, staring at a wall all day.
I certainly can't see how it could be demeaning to 'all other sufferers'.
I can understand that some people may not be comfortable with humour as a coping mechanism but it's certainly applied liberally in my family!
And how good it was to see three sons looking after their dad in such a loving way.