I'm guessing that your Mum and Dad live in Scotland - and if that is so, laws in Scotland are different, so you need responses from people living in your part of the world.
It sounds the same as what in England is called being 'sectioned' under the Mental Health Act. But I may be wrong there.
I have no personal experience of it, because we agreed to a 'voluntary admission' to the assessment unit, but I do understand your Dad's feelings. We (in England) were equally disturbed to discover that our mental health care of older people team - a so-called 'multidisciplinary team' including the social worker on secondment from the regular local authority social services department - could make all and any decisions they chose to make. It was a very uncomfortable experience all round, for the family.
In theory, the professionals are of course supposed to listen to the views of family members and to take those views into their decision-making process, but it's very difficult sometimes to put that theory to good effect.
Once someone comes in touch with social services and/or mental health services for older people, you have in a very big way already handed over control to 'the system'. The decision-maker will always remain the social worker, or the consultant, or similar.
When we were extremely unhappy with a certain decision made by this multidisciplinary team, we were told that if we didn't like it, we would have to take it to court. But, that was in England, and it is not the norm. Sometimes it happens though, and many people are totally unaware of the enormous powers in the hands of social services or similar.
If your compulsory detention/treatment order is anything like the system in England, it requires 'treatment' to be offered for a reason. You can Google the terms, and there are a lot of references and detailed explanations available - all referring to Scotland.
Here's just one:
http://www.scotland.gov.uk/Publications/2008/09/24090333/5
I'm sure those who have experience of them will be able to advise you, but meanwhile I wish you all the best.