My parents hate my boyfriend!

Me and my amazing boyfriend have been together for six months. I'm 18 and he's 16 but we don't mind the age gap it's only two years. But my parents (especially my mother) hate it. They say he's too young and they don't like him but they never tell me why and it's really starting to upset me. He's such a good guy he buys me gifts and treats me like a princess, all of which they know about. He even threw me an 18th birthday party for all me and all my friends. Yet this still doesn't make my parents like him. I don't know what to do. I feel like they still treat me like a child telling me who I can date when I'm an adult now. Am I wrong?