My father with dementia bullies and threatens my 8-year-old. What do I do about my elder father being the abuser?

I also agree with mailman56. Even if you tell a child that grandpa is sick, the child isn't mature enough or life experienced enough to be able to emotionally make that separation even if he says he understands or says okay. The child's self-esteem would be at risk unless you either prevent it from happening or protect him in the moment. You are doing this for your son's sake, not for your father's anyway. Your son has to know he is protected from verbal or physical abuse regardless if the person is sick.

sorry, but even though you tell your child it's the dementia, your son will remember these confrontations. At this point I would bring your son around him only when there are enough people around to take your Dad's concentration off of your son.

How bad is the bullying? Dose your 8 year old understand that its not grandpa doing this, Its the dementia!? They do have counseling to help you and the family with this. And then you need to decide if this is the best thing for him to be in your home with your family. I know this is very hard on you but your kids need to feel safe in there own home too. And sometimes when people with dementia had mean behaviors they can get worse. Even the nicest people with this can get real mean. Its not them its the dementia! Please speak to a counselor and then go from there. Wish you the best and let me know how things go!

when you hear your dad doing this, try changing the subject...get his attention focused on someone or something else.

I agree with mailman56--eight years old is an impressionable age, forming memories that will last a lifetime. It will damage your son if you don't speak up and protect him. Do you know why your Dad is bullying? I would ask him. I think that generation of men did not get the affection and strong male role modeling that it takes to become a nurturing male:(.
I would show lots of affection to your Dad and try to soften him up, and let him know it's OK to be tenderhearted with his Grandson:).

The boy needs to KNOW that you will stand up for him! And back him up whenever he stands up for himself!

This is a deal where you don't care how sick the old man is -- some things are off limits!