Hi Chloe, welcome to TP
To be fair Chloe it's a doctor not the care home that have prescribed this medication so it's s/he you should be talking to about your concerns really if at all possible.
Visitors don't always see the full picture, I spend an half an hour chatting to a woman as she fed her mum, I was feeding my wife at the next table, her mum was (totally out of character) nice as anything. Within 10 minutes of the daughter leaving the usual swearing started, then 10 minutes later she walked down the corridor slapping everyone she walked past (my wife included) then started a fight with a frail old lady with a walking frame.
From what was said I suspect the family will be given 28 days notice to find her somewhere more appropriate to live and all of us that have seen the big picture will breathe a sign of relief as she goes.
The care home have a duty of care to all the resident's including your dad, so if they feel he is a danger then the first option should be get the family to find him somewhere else that can meet his needs not the "chemical cosh".
Other people's experience of a medication isn't really relevant, my wife took one of the ones you mention and it worked well for her, but that proves nothing. Our middle child nearly died first time he was given penicillin, as we found out (the hard way) he has an allergy, some people die from eating a peanut.
I'd try and work with the doctor and the home to find a solution like an alternative medication as the first option and I'd say "it isn't suitable for him because of..." rather than emotive words like "drugged up" that could sound like an allegation which would put them on the defensive, big time, (it's OK to speak your mind on here) but accusing a doctor and a care home of "drugging someone up" won't go down well.
Sorry to go on so much.
K