Ahhh - yes - those parents. I remember them well.
When I was in high school and just beginning to really get into Wicca and Paganism, some Shamanism - I shared it with my best friend. Who of course thinking her mom was the best - went home and shared it with her. Well - mom decided that I was worshipping the devil and was going to take her daughter to hell with me. From that moment on I was not allowed to see my best friend at all outside of school.
MOre over, the guy my best friend was dating was not allowed to see her either - apparently I rubbed off. (I think her mom was just scared she would have sex....whoops - too late already missed that milestone, mom!
I spent the last three years of my high school career finding ways to hang out with my best friend without her mom knowing, arranging meeting with her boyfriend...etc.
She wasn't even allowed to give me a ride home after school or talk to me on the phone!!
When I was a senior our band (yes I was in Marching band - no one make any comments) was going on a trip to CA for the Hollywood Xmas parade. My best friend, her twin and me were going to share a room. We had signed up for a room, and everything was set. Her mom went to the band director told him I was a satanist and that she thought I was a horrible person and that she would pull her daughters out of band before letting them room with me. So instead of moving two people into a different room - he moved me. I spent my senior band trip with a room full of annoying freshmen i didn't like!!!
Mom convinced best friend's sister that I was evil - and sis tried to convert me a lot. Spent a lot of time weeping over my soul and that I wouldn't be able to enjoy the benefits of heaven with her. IN the end sis turned out to be a lot mroe sane when mom's insanity (and mom was nuts) started transferring on to her as well.
This whole thing was so well known in the band that one of my friends, in his senior will, willed my friend's mom a satanic bible. Needless to say - mom didn't think it was terribly funny. I however, I thought it was hysterical!!!
I feel for the poor boy. I went through something similar for three years. It was a bummer. I was stressed out and upset the whole time. I couldn't go to prom with my best friend - cause she wasn't allowed to go with her boyfriend. I couldn't go to a movie with her, or spend the night. I had major verbal fights with her mom (not fun for a high schooler) and had to explain to my teacher that I was not a satanist. Plus she volunteered for the band and was there to chaperone everything that we did. So I had to deal with her a lot.
I think that her mom is one of the major reasons that she and I are no longer friends - (that and a major case of boyfriend mess:LOL)
I don't have any advice - just be supportive and let the boy know - if you can - that you will cover for him or whatever if you would. And make sure your daughter knows that she isn't a horrible person and that it isn't her fault. It can be really hard to think that you are the source of all things bad and wrong - especially at that age. You don't even think about things like this at that age - and then you are being blamed for possibly corrupting someone's immortal soul.
So good luck and be as sane and rational as you can!