You could try correcting them. Of course, this will rarely work. You could try redirecting them to another subject. But the thing is, you are not going to "fix" this.
You never know when a patient is going to become abusive, if it will last, and how bad it will get. The only thing you really can do is the one thing most don't want to hear: medically sedate your loved one.
Now, when you think of medically sedating someone, your first thought is probably of the movie "One Flew Over the Cuckoo's Nest." That's not what you are trying to attain. You don't want them to be in a zombie-like state. That is never the goal. The goal is to get them on medication that will lessen these symptoms of aggression.
Combativeness, anxiety, depression, loneliness and many other emotions go along with dementia. It can take weeks to get the right dose and the right medication to best help your loved one.
Or you may get lucky and the first drug they try will work. You don't want them medicated to the point that they can't function. I am on many different medications for anxiety, depression, and stress. I would not be able to function daily without these, and I don't see one bit of difference in myself.
I don't feel drugged, nor do I feel any different at all. But the people around me can tell. My wife can tell. And I, of course, can tell when I forget to take my medications.
The goal is to find a balance where you can function as a human being, but still have the proper medication and the proper dose that will keep your emotions in check. Even with my medications, I have bad days. We all do, and we always will. But if your loved one has anger issues, you have to deal with them head on because they will only get worse.
Verbal abuse almost always leads to physical abuse. Don't let this happen. You and your loved one have some very rough times ahead. If every time you suggest something like taking a bath, it becomes world war three, with verbal assaults and even physical violence, you need to see their doctor and ask for help.
These people need to be medicated. That is the key. You can't wish this away. There is no magic pill, but there is medication that will help. Nothing will stop the emotions completely. They stem from the brain, which is diseased.