How does a group founded with the goal to do good works wind up as a vehicle for murder and pillage?

To sum it up in a nutshell, it goes like this:

A group is founded with some good intention or other and a policy built around that good intention. The basic purpose and policy drive its actions. It’s a good group, people of good will like it and join it. It’s quite well run so it prospers and gains influence.

The vast majority of human being are sane (i.e., honest and constructive in motivation). They tend to get along and where they form the policy-making bodies of groups or set the group agenda, such groups tend to stay more or less on the rails of their original good intentions.

A small minority of human beings are not sane.They are destructive in intent, even though that intent is often masked.

By "masked" I mean that there is a disparity between what they SAY and what they DO and they will claim the most noble motives while committing the most heinous acts.This confuses honest men of good will who, being of good will, are naturally generous in their opinion of their fellows and assume all their fellows are of good will also. They are consequently often slow to twig what they are actually looking at when they see criminals at work (dead bodies in the streets, cities on fire, children with limbs blown off, little things like that.).

The insane minority are a liability to have around and overtly or covertly tend to mess things up for the sane majority. They are, in other words, criminal.

The criminal minority, being criminal, do not baulk at deceit, or theft or worse. They too assume that others are of similar inclination to themselves and conceive of their fellows as untrustworthy and dangerous.

When an honest group prospers and gains influence, the criminal is attracted to it for the opportunities it presents to carry out criminal works such as a.) get rich without the inconvenience of having to earn it b.) become powerful; c.) inhibit, restrict or destroy others.

That group might be a religion, a political group, a government, police force and so forth. If devious and clever enough, the criminal can pull off his primary objective: the achievement of a powerful and influential position within the group. He then has the resources and channels of influence of the group at his disposal for the achievement of his own nefarious goals.

This does not mean that all men in powerful positions are criminals, the majority are not. However, those positions are flames to a moth and where a criminal personality does get himself into such a position, the rest of humanity is in trouble. The Spanish Inquisition is one primary example. I’m sure you can think of plenty of contemporary examples.

Once in influential positions, the criminal can strengthen his own position and weaken those of more decently motivated men. He is not hampered by qualms about Truth, Honesty or the need to respect the rights of others.

When a criminal or group of criminals gain control of the executive body of a group and are able to alter or reinterpret its policies ("What Jesus really meant when he said love thy neighbor was……") and dictate its actions, the group will then act as a criminal group. The group becomes a criminal group even though the majority of its members are sane men and NOT criminal.

The criminals that have seized control of the group’s agenda engage in all manner of deceit, false reports, and reinterpretations of original policy to justify whatever criminal enterprise they now wish the group to engage in, such as the murder of "unbelievers" and seizure of their property, the invasion of a foreign country to nick its gold/ food/women/oil etc.

Original policy and the original founding spirit of the group become reinterpreted, explained away, edited out of the scriptures, obscured by gobbledygook, taken out of context and what-have-you.

The sane members of the group become very confused and start to feel a bit batty themselves.

The sane man finds himself, without quite ever understanding how it ended up that way, in a war where he is expected to kill other human beings he has never met in the name of a god who told him repeatedly (or so he thought) not to kill.

Summary

Where a group has moved away from its original ethos and towards a more violent, covetous or morally lax position, you know that criminals have moved in on and suborned its policy-making, agenda-setting bodies.

A handful of criminals can thus wind up controlling a nation of millions of honest people. Such a nation will engage in criminal acts such as murder and mayhem that are normally anathema to the basic social instincts, mores and customs of the majority of its members.

Thus a group can act insane when the vast majority of its members are sane. It can act criminal even though most of its members are honest people. It can engage in mass slaughter even though the majority of its people would not so much as kick a dog.

Thus humanity as a whole can appear insane even while the vast majority of human beings are sane.

Having found themselves party to acts they know are wrong, good men begin to feel degraded. The nation or race loses pride in itself and begins to decay.

Humanity is not bestial, savage or criminal. But a small minority of its members are. Man’s weakness lies in his inability to detect and keep from power that small minority.

And herein lies an answer to war and to the instability and short-lived nature of civilizations