I think you have tried to be reasonable but whatever you say he will not accept it mainly because he is ignorant of understanding and finding out about the reality of his dad's stage of dementia and not willing to understand or accept the risk and impact on your mum.
I would say...
Firstly... If he loved his dad he would do what is in his best interests and put his strong unreasonable incorrect and selfish thoughts to one side and in that case he should move his dad in with him with 24 hour care not a part time care package. He won't do this of course!
Secondly..just go ahead and do what is the right thing for your mum. Enough discussion...you will never win with this individual. He clearly has no regard for your mum's welfare.He is worse than the idiot he is... he is an extremely selfish manipulative bully. Don't let him do it under any circumstances. If your mum I would also be speaking to the manager about the fact that as his wife she is next of kin and talk to them about his intervention.
I would say...
Firstly... If he loved his dad he would do what is in his best interests and put his strong unreasonable incorrect and selfish thoughts to one side and in that case he should move his dad in with him with 24 hour care not a part time care package. He won't do this of course!
Secondly..just go ahead and do what is the right thing for your mum. Enough discussion...you will never win with this individual. He clearly has no regard for your mum's welfare.He is worse than the idiot he is... he is an extremely selfish manipulative bully. Don't let him do it under any circumstances. If your mum I would also be speaking to the manager about the fact that as his wife she is next of kin and talk to them about his intervention.