Hello,
I see that you are 15 years old and parents make decisions for you. If you really want to watch a movie with him, perhaps you can suggest to your mom if you can have a girlfriend or a sister for chaperone.
If they really object, I don't think you can force them to allow you to go. What about inviting him to your house and watch a movie with him with everybody around. That way, they can observe him and hopefully get to know him better.
Hope this helps.