It's unfortunate but there are many people that function in very rigid black and white opinions. This shows up in politics, religion, and believing that all X's are bad. Yes a lot of people carry very prejudice mindsets. And yes, a person that is prejudice like this can be a parent unfortunately and can express anger and resentment if you disagree with them and want to have your own opinions. It's often a waste of time to change a person like this too, so all you can do is avoid discussing these issues with them and distance as much as you can.