He just watches what people are doing while watching tv programs. Irritated whenever somebody he doesn't like do the laundry or do something in the kitchen. He complains about the smell of the food which he didn't do before. Talking nonsense or butting in whenever somebody's talking or we have a visitor.
If he doesn't like certain smells, then try to avoid cooking those foods. If he interrupts guests conversations, I would encourage them to be patient. If he really seems to upset him, then allow him to stay in his room for a short while, but leaving him there for long periods on a regular basis doesn't seem fair to me.
I know how difficult it can be. My cousin was very draining with repeated comments, rambling, confusion, questions, etc. while in her home, but you have to deal with it and not by excluding the loved one to a room by themselves. , IMO. I also think that the social interaction is important to encourage for as long as possible. For some reason I've read that is very important.
I hope he also has opportunity to interact with the household, even if he doesn't make sense, and that he gets a change of scenery throughout the day, perhaps watching what is going on out the front window, watching a bird feeding station out back, etc.
Have you tried activities other than watching tv for him? Can he fold towels? Match socks from the laundry? Sort coins? Does he do crosswords or jigsaws?
Don't get me wrong ,,, I think watching television is perfectly OK. When my husband first had dementia his attention span was so limited he couldn't enjoy that and it was something to celebrate when he improved enough to enjoy television sometimes. But a little more pleasant stimulation might be a good thing.
Corinne, there is no getting around that living with someone who has dementia involves conflicts. I suggest compromise by having your loved one in his room at certain times, and learning to shrug off the conflicts the rest of the time.