How to tell my parents their friend makes me uncomfortable?

tl;dr My dad's childhood best friend kept trying to get me to masturbate on his motorcycle, I'm reluctant to tell my parents because it happened awhile ago, subject is awkward to bring up, I don't know what they would do about it anyway, he didn't technically do anything to me, I was too intimidated to tell him to stop, and I'm an adult (I was 20 at the time, he's early 50s).

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It was my dad's childhood best friend. I was 20, he's early 50s. He's never really been creepy around me before but I didn't really see him a whole lot when I lived at home. Now that I'm away at college my parents hang out with him a lot more.

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He came over to my parents one day over the summer, don't remember why, it was some sort of special occasion. I kept getting some sort of weird vibe from him but I didn't really recognize it as creepy until later. Anyway he offers to take me out on his motorcycle and I accepted because I like motorcycles. First he kept asking about my long-distance boyfriend. Then he kept asking if I was on birth control because "I don't want to assume but your boyfriend is 24". He kept saying he would get it for me if i wanted because he "knows how my parents are" (read: super religious, raised me to wait until marriage). I was really uncomfortable but assumed he meant well, never answered any of his questions. And then he kept talking about why women supposedly like Harley Davidson Motorcycles. And it's because they vibrate a lot. and he kept talking about how he took one of my parents' friends out on the bike a couple weeks ago and she was screaming because apparently the motorcycle vibrations made her orgasm so hard or something I don't know. And he kept telling me I'd really feel it if I leaned forward. And how I must be missing my boyfriend. And how it must be lonely with not getting to see my boyfriend most of the summer. And that he really didn't mind if I did. And he wouldn't tell my parents. And he kept asking if i was leaning forward yet and he kept hitting the accelerator so the engine would vibrate harder. And I was so uncomfortable and I wasn't answering any of his questions and I feel like I was obviously uncomfortable and I was leaning as far back away from him as possible. And I was honestly kind of scared because I was stuck on the back of a motorcycle with him. And I've basically avoided thinking about it ever since. 

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He texted me the next day asking if I enjoyed the ride and that he hoped I wasn't uncomfortable. I never replied. It took me 5 months to ever tell my boyfriend about it. He was going to tell my parents for me but we broke up right after and are still deep in the hurt post-break-up stage.

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I don't know what to do. I reluctant to tell my parents, it's going to be super awkward to bring up, a taboo subject in my extremely Christian home, and it's taken me more than 5 months to decide I should probably tell them about it. I signed up to meet with someone at my college's counseling center but their first opening isn't until the end of January. Just need support and advice for talking to my parents.