Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, says the Lord. - Rom 12:19
This verse is from a passage (Rom 12:14-21) intended for us to avoid selfish personal behaviour. When you represent a group and your actions are on behalf of the group, it is not selfish but causal.
In that situation it falls under the auspices of government which, if good, protects its good people from those who are evil.
Criminal justice system and national defense are examples.
Greater love has no man than this, that a man lay down his life for his friends. - Joh 15:13
This is what our armed services do. They lay down their lives for friends.
In the same vein it is also justified for the group to push back against persecution since it is acting on behalf of others.
It is never acceptable to push back on personal persecution.
It is necessary to make this point because we sometimes extrapolate personal instructions for group instructions and that is not generally the right thing to do.
America is the product of Christian's fighting for the good of the Colonists. The U.S. defeated Germany on behalf of the people of the world.
So, in the time that we are living it is important to take stands to protect others and to fight as needed against those who come against the group.
I guess Christian pacifists would reject this argument but they would not be alive now to do so were it not for those who fought the enemy so that they could live.