Homophobia

So my parents are trying to invite their racist and homophonic parent that we have had no contact with in years to our house while they are in town. They have said some very purposely hurtful things to a member of our family and never apologized. I tried to tell my parents that they shouldn’t be welcome in our home and if THEY want to see them they should go to a restaurant. What should I do? These are not nice people. I know they are technically my grandparents but I don’t like them and choose to have no relationship with them after the shit they pulled.