moderation will never stamp out but the tiniest of hate/ignorance that will come. the only thing that will work is removing the one thing the trolls feed on... your reaction.
I think calling these people trolls misses a significant point that they feel their grievances are genuine. See a bunch of the comments below defending abuse as a legitimate response. This is way more about cultural norms in terms of what is an acceptable way to communicate and moderation is supremely effective at establishing them.
Hate and abuse are definitely hard or impossible to eradicate completely but we can do a lot better than current social media platforms and places like the Steam forums are doing.
Moderation is essential because by publicly making an example of trolls, you can change the culture to prevent it. It's the same theory as patching up broken windows to ensure that worse things don't happen.
I feel internet shaming is the wrong answer as it's a different side of the same coin. As much as these people are trying to tear down and essentially bully people with words in a negative manner -- those who shame those people end up doing the same thing back, and often take it to extremes where punishment is vastly out of touch with the "crime".
By shining a light on these groups you attract others to it. This is why (I personally feel) the extreme right and extreme left exist today in politics. When you highlight (even to shame) a group it galvanizes them and brings other loonies to their cause.
I'm not talking about shaming people, I think that if you want to have a community that doesn't have abuse then you need the admins to remove or ban the people who post abuse and threats.
Hate and abuse are definitely hard or impossible to eradicate completely but we can do a lot better than current social media platforms and places like the Steam forums are doing.