How can I make my boyfriends Lebanese parents like me?

I've been dating my Lebanese boyfriend for 4 years now. We started dating after high school graduation and soon we'll be graduating from college. We have an amazing relationship and love each other a lot, but his parents don't approve of us dating at all. We're both Catholic, so religion isn't the issue. His parents are constantly nagging him about school and if he gets a bad grade(which isn't that often) it's automatically my fault. They don't believe he should be in a relationship until after he finishes dental school. I know they don't like me and it hurts my feelings, especially when my boyfriend covers up for them or defends them...which I'm pretty sure he rarely does for me. He's very intimidated by his parents and pretty much does everything they tell him to, except dump me. I understand that family comes first and he wants to be respectful, but I think his parents behavior towards me is ridiculous, especially since we've been happily together for 4 years. I want him to confront them about it but I feel like he never will. How can I make his parents like me more? When they drive down to visit my boyfriend they don't even want to see me. I don't know what to do or how to convince him to confront his parents about their rude behavior without him getting all defensive about his family. Any advice????