Dilemma

I'm in a bit of a pickle right now, and need some advice. I'm in a community that is normally very amicable, but has a member who refuses to play by the rules, has a history of maliciously sabotaging the group, and ignores requests to leave. I was just tipped off to some unsavory evidence that could destroy this member, and the person who sent it to me said he wasn't sure what to do with it. I'm not sure who else might have the same access, so I am working on a possibly lit fuse.
On one hand, this person has refused to respect the rules and subsequent requests to leave; the evidence I have could easily be used in a speak-softly-and-carry-a-big-stick fashion in order to ensure a quiet exit. On the converse, I have access some sensitive material that's already eroded my opinion of this provocateur. I can't destroy all the evidence since it's been proliferated online.
In the interests of anonymity, I won't disclose any more information regarding this (don't worry it's not anything on a national level, but some people here might know this group or the persons involved).
Any advice?

Hmmmm ..... Perhaps make a list of everything he/she has done wrong and show him/her this list, then ask them, dude, if you're not gonna be part of the group, why are you here. Then they will either leave, be stubborn and ignore you or ask for a change in the rules, which i guess is kinda fair.

This isn't really advice Rex and it may not ultimately be applicable in this dilemma - but in these kinds of situations this story can lend a different perspective:

“From the seventh century, Buddhism flourished in Tibet, but in the ninth century, it declined as a result of a ruthless Tibetan king who aimed to destroy Buddhism in his country. Then, in the early eleventh century, Tibetan Buddhism began a regeneration. This was marked by increased travel between Tibet and India, as key Tibetans traveled to India for instruction, and many Indian masters were invited to Tibet. Foremost of these Indian masters was Lama Atisha, a well-known scholar and practitioner who was one of India’s principal teachers of mind training. Lama Aisha was invited personally by the current king to spearhead the reestablishing of Tibet’s rich Buddhist cultural and religious tradition. Initially, Atisha committed to staying in Tibet for three years, but he was so well-loved by Tibetans that he remained for a total of twelve years, finally passing away in Tibet.

One Reason for Atisha’s long initial commitment was because travel from India to Tibet was not easy. You had to negotiate hot, disease-infested jungles, eighteen-thousand-foot Himalayan passes, and inhospitable tribes and bandits. The trip took months to prepare and months to complete, involving dangers and hardships we can barely imagine today. Among the party traveling to Tibet was Atisha’s personal cook, who was known as a very difficult person to get along with. And indeed, the Tibetans found him rude, crass, and unfriendly. But even worse, the cook’s terrible behavior did not merely extend to the Tibetans but even to Atisha himself. The Tibetans just could not understand why Lama Atisha would keep such an unsavory person as his cook. Wasn’t travel hard enough?

However, Atisha never showed any sense of intolerance, anger, or embarrassment over his cook’s behavior. Then as now, traveling can sometimes bring out the worst in people, and the Tibetans were impressed that Atisha showed only affection for the cook. Finally, though, they couldn’t sand it, and they asked Atisha why he did not fire the man and send him back to India. Lama Atisha replied, “He is not just my cook; he is my teacher of patience.”

With that one simple statement, Lama Atisha demonstrated to the Tibetans and to us the entire concept of transforming one’s inner experience through mind training.”

I'll ask you a question... regardless of your behaviour on the internet, how would you feel if someone released sensitive information on you, information perhaps completely irrelevant to your attendance here, for example? If I were in your place, I would deal with their behaviour on my site, and only that, using whatever rules your site has set up to deal with people who cause problems for other members... everything else, wouldn't be my business, and I'd leave it be.

There's a significant part of me that believes that you should deal with evil and harmful behavior swiftly and with whatever tools you have. We are after all charged with the defense and protection of others.

But there are also the questions of "Is this the right or best way to resolve this?" And "What gives me the right to decide this course of action?"

If you're questioning whether it's the right thing to do, it probably isn't.

If this person can't be convinced to cease their malicious behavior, refuses requests to leave, and refuses to operate by the rules of the group, then they have no place within that group. If their behavior has already made others want them out of the group, then what difference would the introduction of that information you have really make? If it's something terrible like murder or rape, I think you have an obligation to present that information to authorities. But if they're just being a nuisance and the members of your group already want the person gone, maybe you should discuss possible legal action with your group to remove the member who is being problematic.

Is there no way to actively cut this person out? To block them from having an online presence in the community, or to contact law enforcement or have a restraining order put in place if it's a physical disruption?

Thanks guys for the responses. Yeah, this person just keeps popping back in (and there's really no way to physically stop them), so I decided the best course of action was to hand over the evidence to the official leader of our group (even though they've been powerless to stop this person). I never would want to publicly reveal what I've seen, so I talked to the person and politely asked them to leave without mentioning the material.
Loudzoo, I appreciate that proverb, if I see them as a problem or opportunity, that's what they'll be.
Ultimately, as I'm not the only person affected by this, I will not act upon it, but ensure those with the proper authority are able to in good faith.
Thanks TOTJO!