Advice Needed: Break-Up Problems

I really would appreciate your advice about how I should handle the situation. I think I'm just WAY too involved in the situation that I can't see the simple, logical solution. Thank you!

THE SITUATION:
My friend Jane* recently broke up with her boyfriend John*. The break-up, overall, was a nice one. John simply told Jane that he thinks it would be best if the two of them were simply friends.

Jane's father is angry at John because John's sister told Jane that John said, "My relationship with Jane is simply experimental--to see how well I interact with girls."

THE PROBLEM:
Jane told her father John said the relationship was only experimental. She didn't tell her father that John didn't actually say those words--it was his sister. To top it off, though, Jane doesn't even know if John's sister is telling to truth.

Based onto a "he-said-she-said", Jane's father is out to ruin John and make his life a living hell.

MY PROBLEM:
I want to be there for Jane because she's one of my best friends, but I don't agree with what her father is trying to do to John--especially since his hatred towards John is based on a rumor. I believe that Jane still has some kind of feelings towards John, but is currently clouded by her anger and sorrow. Because of this, she doesn't tell her parents the whole truth about the John saying the relationship was only experimental. I know she doesn't want something physical to happen to John, but I fear that's something that can happen. Jane's father has told everyone he knew what John supposedly said, and they are extremely pissed off.

I want to tell Jane that she has to tell her dad the full story of how the break-up went down, but because Jane once thought that I was trying to take John away from her (because the two didn't talk at all and I actually talked to him because I has class with him), I don't think I'm the right person to do so. I really don't want her to think I'm trying to defend John because I like him in a romantic way, but I can't completely support her knowing that her father is threatening and trying to destroy someone else's life. I know he's hurt about his daughter being so crushed, but it's just morally wrong for me, and I think it's childish what her father is trying to do!

EXTRA INFO:
We're only in high school. Jane is an only child. John is (in my opinion) anti-social. This is John and Jane's first relationship. Jane's the only one in our little trio (Jane, Jane 2 and me) who's been in a relationship.