Honor Among Thieves. It’s a common phrase that has been around for a long time. But why? Are thieves the only honorable people? Is there something special about thieves?
Humans have had hundreds of thousands of years of evolution to train us to form groups. There is safety in being part of a group. It’s unwise to betray someone in your group.
Thus I think you’ll find “honor among any group”.
There are a lot of dishonorable groups, MDs, attorneys, realtors, auto mechanics, politicians, etc but self preservation tends to keep them from stabbing each other in the back unless they are perceived as competitors (thus not actually part of the group of the other person).
Could we perhaps break away from our small tribe mentality and perhaps somehow accept that we are members of the group of entities living on the Earth? Thus it is in our best interests to take care of each other (including animals).
I've always interpreted the the expression to mean that thieves are generally not honorable. Stealing for a living isn't honorable. Thieves are generally quick to steal from one another just as they would steal from anyone else. However, they have some lines that they won't cross with one another even though they would cross those lines with anyone else.
I don't think that the expression is meant to say that everyone is honorable within his or her own group. Most people are fairly honorable as a general approach to life. For them to be honorable within their own groups is just an extension of their being honorable overall.
I also see the expression as describing a bit of a mutually-assured destruction. Even within groups of people who are not honorable, going beyond certain lines is dangerous because crossing those lines leads so easily to mutually-assured destruction. If one thief gives law enforcement some piece of information to try to hurt a rival thief, the rival thief might give law enforcement the same kind of information in the other direction. The result will be both thieves and maybe many other thieves being taken down at the same time. No matter how much they hate one another, the thieves don't want to cross those lines and destroy themselves.
Life is just not set up so that we are all in this together. All of humanity will never be our core group. All of life will never be our core group. Honor should mean that we don't go beyond certain bounds with anyone.
We are not all the same groups, and can never be. There will always be different goals for different people, those will be in competition. Groups will always see people who are getting resources for their goals they feel would better be used on the goals that they have. These things can not be avoided. The more that difference are ignored, the greater the likelihood that the differences turn into bloodshed