This thread is an uncomfortable read.
I am really worried how many people are insisting that OP should not query this and simply accept that it must be right, appropriate and in dad's interests, simply because the care home are doing it.
Do you honestly believe that there is never abuse (either intentional or through incompetence?) in care homes? That it's right to advise the families of loved ones in care homes to ignore any concerns they have about their loved one's well-being, because the care home is always right?
The way some of you speak of those with dementia is also quite distressing, to be honest. As if they are simply a problem to be solved, by any means possible. No consideration or regard for their well-being, or sense of privacy and dignity.
You are also ignoring the fact that OP was one of her dad's main carers. Better than almost anyone, she knows him and his needs. If the care home has truly had such a negative impact on his wellbeing, that he has gone from a man who could mostly go to the loo independently, to a man who requires 4 people present while this happens.... Then she needs to ask why, and whether this is an appropriate placement for him.
I don't have experience of patients with dementia in general, and nor did I need it. I had detailed experience of my own father, a dementia sufferer. While he was alive, I was his carer for ten years, and thus an expert on his needs. I was able with total confidence to assess care he was given by others, and judge whether it was appropriate or not, an unnecessary afront to his dignity or not. Much more so than strangers on the internet, and more so too than care workers who had only known him a month or two.
I would suggest the same is true of OP. And she needs to act to protect her father. While dementia patients may have a whole range of cognitive and physical struggles, which may in some cases provide challenges to others, they have just as much right to privacy, dignity, consideration and kindness, as any other human.