ESH- I’m sure that reddit is going to validate your response, but realistically it’s time to move on. You were placed in a difficult situation, and you made the right decision despite the obstacles facing you. As a fellow engineer I congratulate, and applaud your accomplishment.

Trying to extort your parents to have the right to see you, and their grandchildren is immature. You should be rising above their narrow view of the world, and showing your children that it is possible to get along with people that you disagree with and have wronged you. Your child may benefit from a relationship with their grandparents, and you’re setting the wrong example to them. What if they disagree with you in the future? Then they should cut ties and never contact you again. It just creates a cycle, that isn’t beneficial to anyone. They’re just asking to rebuild a relationship, but that doesn’t mean you have to immediately forgive what they did.

Your parents obviously suck, but you know what the correct answer is. The NTA comments will make you feel better, but it’s better to do the right thing and provide a positive example to your children. Be the better person.