I want to insult my religious dad
What is the reasoning behind insulting him?
For not following his word on leaving my first girlfriend whom he thought was the right one, for marrying my mom whom he had an affair with
I'm sorry that your dad made lots of mistakes throughout his life, but he's following religion because he needs guidance for his wrongdoings. It's mean to constantly kick him down for his mistakes, you need to be kinder and more understanding to have a healthy relationship.
Screw him. He deserves it.
I do not think that your dad deserves that treatment, you should not try to insult him. Everyone makes mistakes, even me and you.