Dear Amy: Over 20 years ago, my middle school-aged younger sibling was violently sexually assaulted by the adult son of my parents' best friends.

When my sibling told me, I convinced my sibling to tell our mother, assuming she would do the right thing. But not only did my mother refuse to take any action, she forbade either one of us from telling anyone: cops, school counselors, even our dad.

I live with great shame that I did nothing more to help my sibling, but I was a minor, too, and didn't know any better.

Fast-forward two decades, and my sibling and I are well-adjusted adults with loving spouses and families.

My spouse and I are active in the geek culture scene and attend a few gaming/comic/geek conventions annually.

My sibling's abuser is also a frequent patron of these events. Every time I see him, I want to tell site security that he's a predator, but legally have no grounds to do so, since he's never been convicted or charged for what he did.

Instead, I keep watch, to try to ensure that he's not luring some poor child off-site.

I can think of no other viable course of action. Can you?

Amy says: First, check and see if this man is on the sex offender registry. Each state maintains one, and the FBI compiles these into a national database. Check your state, or search fbi.gov/scams-and-safety/sex-offender-registry. If he is on this list, you should absolutely notify the security team at the convention site.

You should contact your sibling to see if they want to try to pursue legal action against the perpetrator. Rainn.org offers state-by-state information about the statute of limitations for sexual crimes. Even after all this time, your sibling could choose to try to report this attack to the police. Another option is to try to sue for damages.

You and your spouse and/or your sibling could choose to personally confront him. The safest option would be to reach out through a private message. Tell him that you know what he did to your sibling, and advise him that you don't think it's prudent for him to attend conventions where there are children present. Do not threaten him.

You and your sibling should also talk about this — ideally with a counselor. You are both survivors of an attack that shattered your trust. I hope you can work this through, understanding that when parents fail to protect or defend their children, children are left to carry the burden.

Opinion not popular

Dear Amy: I would classify myself as a generally nice, nonjudgmental friend.

Recently I was having what I thought was a benign conversation with a group of friends. I expressed my viewpoint that I wouldn't want to date a person who was super into spectator sports. This was met with anger, disbelief and harsh criticism.

I always try to give my friends the benefit of the doubt and accept their opinions (even if I don't agree), but now I'm feeling judged for not fitting into the group's majority opinion on this topic.

I want to bring up how I'm feeling and address the larger issue (I don't care so much about the opinion as I do the reaction), but want to make sure I'm not creating more hostility. How would you go about this?

Amy says: It's best to respond (if possible, with humor) in the moment: "Whoa, ease up, guys. I feel like I'm on a bad Tinder date, here!"

After the fact, you can express: "I've been thinking a lot about this, and while I respect that we don't agree on some things, I left our last meeting feeling like you all really piled on."

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Send questions to Amy Dickinson at askamy@ amydickinson.com.