Groups rally when they're being attacked.
Groups rally when they're being ignored (and have a spark).
If you want to make your group stronger, foster the perception that the group is being attacked. They bond under fire. They support and help one another.
Smart group organizers know this. They bait an opponent until they react and then capture the moment for others to see.
If you want to make your group louder, foster the perception that they're being ignored. Create plausible actions they can. Targeting an organization's sponsors, customers, or writing to their employees often works. Never highlight a problem unless you have a solution.
Better yet, collaborate on something (e.g. how to switch to a new customer) and begin disseminating it. Turn that frustration of being ignored into something the group can productively do to feel they have power.
Highlight a particular person whose attention they need to get and go about getting it. Take steps to to ensure they can't be ignored. Phone them up 20 times a day. Then make it 50.
On the flip side.
Never allow the perception that you're attacking a group (or worse, a member of that group). The entire group will rally against you. Never ignore the vocal demands of a group that has a spark (something beyond normal issues_.
And if you do, there is only one way to dispel an angry group. You're not going to like it. You need to completely engage. You need to let them win. You need them to feel that they have achieved something.
You need to ask them to put forward people to speak on their behalf and then have real dialogue with these people. The symbology of this matters almost as much as the outcome.