My weird family 2

It's been 15 days since my first post about my strange family. During this time, a meeting of my dad's family members took place.

That day, Dad insisted that I go with him, but I refused, saying that I didn't really want to deal with anyone from your family. He understood me and left alone. After the meeting, he said that I should definitely invite his mom to my graduation.

By the way, my graduation will be in June, and my parents and grandmother on my mother's side are invited to it. Dad said it was very disrespectful to his mom that I wouldn't invite her. I said I didn't want to call her, because she wasn't involved in my upbringing, and she always humiliated me and my mom. Dad said that I should start respecting my grandmother, and I should learn to think before saying anything about the family.

Honestly, I do not know at what point in my life I should have started to respect her, since this man did a lot of bad things in my life for me, my older brothers and my mother. I don't know exactly how to tell Dad that this person is not someone who should be respected in principle. Please help me with some advice