Soccer hooligans aren’t exactly a peaceful bunch. Other groups can assemble in a war (e.g. soldiers) and end up as peaceful clubs. The trajectories from/to violent/peaceful aren’t set in stone.
How much of it is because of external pressures? How can they be led to abandoning these things and doing something else instead? Can their support for that other developer group be leveraged?
That’s what makes the situation so complicated. An initial minor skirmish where nobody can say anymore who shot first, or what can be considered an over-the-threshold event for a reaction. An otherwise minor affair nuke-shroomed up (and then the threats appeared) in few days, don’t ask me why, possibly as a result of enough people primed for “something” and then getting this to focus on.
The wagons-circling is happening on both sides and each side has its reasons. And the group-belonging is likely to be a strong motive for both sides.
My guess for the correct response is addressing individual attackers, not the group as a whole. Do not bomb out the whole village just because it hides a few individuals; that will only cause collateral damage and make you more adversaries to counter in next round. Something should be done but be VERY careful about the reaction to not make it yet worse.
…which won’t happen because of too many hotheads. Like in the doomed War on Terror. So many parallels.
My guess is that the group formed out of latent need of the members to belong to a group, the cause (and the demography of the initial group) being close to some, then others snowballed onto it due to some sort of identification that was good enough to provide the in-group feeling, and now we are where we are.
In terrorist groups, there is a common phenomenon of individuals migrating between groups. The groups can even have entirely different goals; the in-group acceptance seems to be a more important factor than the group’s own goals. Don’t ask me for the link, I read that whitepaper years ago and forgot details. 
Yes, but less emotionally. Leave the overly affective reactions to the other side, it will weaken them as well as it would weaken you.
I have a rule to not post when excited, in either way. And it helps a lot to keep cool head and not escalate conflicts Just Because of Feelings. Feelings lie and are fed not primarily by reality but by in-group ties and other subjective factors, and personal traumas of all kinds may (and do) lead to irrationally strong responses. With that setup, the progression into the all-too-familiar internet shouting matches and snowballing outrages is only natural.
(Also, another concept I employ is to favor the less controversial explanation when something offers more choices of interpretation. Getting outraged is tempting, group-strengthening when shared (likely a factor why I find it hard to belong to a group as I refuse to get emotional unless the situation REALLY deserves it, and it rarely does), and, more often than not, wrong, due to the omnipresent risk of mere misunderstanding. If the other side wants to push things, they will repeat the attempt and make it clear.)
Again, generally true but care has to be taken to hear some of the opposition voices. There may be parts of the whole thing where even “the enemy” can be right. The loudness of the yell is not any good indicator of truth of the argument. Listening to the adversary both builds bridges and provides better arguments.
They won’t. And they are sort of needed in a diminutive size and reduced to pretty much harmless as an indicator of the social climate. Membership growth can be an early indicator of something somewhere going wrong. Push them too much underground and you lose these easily observable indicators.
THIS!!! Straight on the money.
Wanting blood instead of striving for peace is a typical maladaptive reaction. Feels good. Does not help.
