A friend's parents are refusing to let me see him because they think I'm a bad influence, what do I do?

I recently befriended a boy who I took classes with, he's 18 (I'm 17) and since summer started two weeks ago his parents have let him out of the house 3 times to be with friends. I was with him all three of those times, met both parents and everything seemed to be fine. Yesterday I went to his hockey game with his dad because I was just fed up of not seeing him and spending the hour talking with his dad (which turned out to be not at all awkward, I thought it went well) was worth the 20 or so minutes I spent with him. Everything seemed fine, I thought I made a good impression, I'm going to a good college, I volunteer at a local wildlife sanctuary, I danced ballet for years, (his dad and I discussed all fo this) etc. When we got to his house I hugged him goodbye and he jokingly pushed me away saying that his older brother was probably watching and I should go. Even though he was kidding there was an odd sense of urgency in his voice so I left. Today we find out that his older brother (30) went through his text messages, we're flirty and I said that his older brother seemed controlling, other than that there's nothing in the messages. This morning his brother and father told him he's not allowed to even speak to me because I'm a bad influence (I have a tattoo and nose piercing). I dress modestly though and I've never ever had a problem with parents before, usually they love me. What do I do I really want to fix this? I don't want to sneak around or alienate him from his parents, but he and I both don't want to give up the friendship.