I live with my Grandma who has moderate Dementia. She is a mean mean woman now, yells at people cusses,is just fairly volatile....at times. Sometimes she is this way and other times she is like tthe sweet lady I grew up with.
You have to remember they have a disease. It develops over time and gets worse.
When my grandma is being hurtful, I turn the other cheek. Cause I know she doesn't mean it and in less rhan 10 minutes, she wont remember saying it.
As much as I'd like to lash back, its not right. She is an 80 year old woman and yelling at her does nothing bit hurt us both. She deserves respect, she has seen wars,depressions and other horrible things, lost her 2 sons and her husband in her lifetime.
If you have a volatile relationship with tour grandpa, then don't go see him or if you have to go, don't respond negatively, change the subject or walk away but don't yell at him. He deserves your respect unless he did something horrible to you in your life.