I worked out as a teen that friendship was going to be key to my ethics and that I would start from an assumption of loyalty to my friends. It's still the place I start from when dealing with conflict or difficulty and it's become a more pertinent issue with social media.

If someone is upsetting a true friend of mine, I will ditch them in a heartbeat. 

Of course there are all kinds of issues around this. I think the majority of people probably act from this basis but not necessarily having considered it. We defend our friends, but at what point is a line crossed? When do we admit that we may have misjudged them? How much do we need to hear to admit that the friend we've been loyal to is a bully, an abuser, a rapist?

It doesn't reflect well on us if our friends turn out to be terrible people. It means either we might be terrible too, or we might be foolish, easily hoodwinked, or poor judges of character. There's a loss of self inherent in admitting that someone you were invested in is actually a bit shit. From experience, it's easier to do this when you aren't the only one. A community ejecting a person can be a lot stronger and more confident than a lone individual doing it.

But then we have to ask questions about scapegoating. We have to check very carefully that the person being pushed out is the person who should leave. Bullies can be really good at playing the victim, and this kind of conflict can turn out to be a popularity contest. The confident attractive, powerful, socially able person is likely to win if they go up against a nervous, fragile, awkward person. Bullies can be charming for the benefit of their supporters, and they know how to pick a good victim.

Staying out of a conflict is always supportive of the abuser, if there is one. Assuming it's six of one and half a dozen of the other always supports the bully, if there is one. Assuming that our friends are good people can make us wilfully oblivious to the harm they do. If we don't police our communities, we give opportunities to bullies, abusers and predators. If we do police our communities, we run the risk of supporting the charismatic psychopaths at the expense of victims who have been chosen because they weren't socially attractive in the first place.

There are no simple answers here. Blind faith in each other is dangerous. Being too quick to believe the worst of someone destroys relationships. There will always be haters. Who are you going to trust? Whose behaviour is going to be part of your reputation? Where do you draw lines? At what point do you decide that a friend is in fact a problem?