"And when the people complained, it displeased the LORD: and the LORD heard it; and his anger was kindled; and the fire of the LORD burnt among them, and consumed them that were in the uttermost parts of the camp." (Numbers 11:1).
In any community or company, complainers always move to the outer edge; especially once they decide to speak their mind. For it gives them an easy access to a quick departure. They can take their shot and get out of there before anybody has any chance to fire back. That's a cowardly thing to do.
And the Lord does not let such a thing go unanswered.
You've heard the old saying, "Fight fire with fire." It's how firefighters stop a raging fire from spreading. The Lord did the same thing in the wilderness journey of the Israelites.
A group of spineless cowards set themselves on the outer edge and began stirring up strife and inflaming people's fears. Their complaints, which tapped into the unspoken feelings of many who were genuinely perplexed by the way things were going on their journey, set off a fire that would surely rip through the whole mass of people if left unanswered. So the Lord answered.
He fought fire with fire. His fire won.
The moral of the story here is do not complain in a position of cowardice, but speak your mind with honor; being open to the possibility that you may be wrong, even though you suppose you are right.
The Lord has no problem with open and honest questions, nor is He put off by the genuine misgivings and concerns we feel when things do not seem to be working out as we hoped. But He does take issue with the undermining activity of those who sow discord among brothers, stir up strife in community, and cause rebellion against those in authority. Especially when the instigators, though posing as champions of truth and justice, are in fact cowards to the core.
This may be helpful to you in a day when opinions and complaints make up the bulk of our public discourse.