Look at the way you present yourself and act. Try to figure out why these people hate you. Maybe they don't take you seriously or they think you are a bad influence. If you care about your girlfriend, show her parents by treating her and her parents with respect.
my parents hate my bf because he acts too friendly with them (making jokes, etc). they dont want you to be their friend. they want to see that u are smart and responsible. u have to act super polite, almost professional.
You should keep trying to get them to like you. Try to find out what they do not like about you and work on that area. make sure you are always polite around them and treat their daughter right. It may take time but they should begin to like you soon.
