Chop off what's rotten

A friend asked me how I'm able to just IGNORE and remove a person from my circle, without emotion. I then told her the story.
If we have a limb that's rotting, the hospital would want to amputate i.e. chop it off. Because leaving it would mean subjecting the rest of the 'good' body to be poisoned by whatever's that causing the rot - gangrene. Gangrene means tissue death which will be followed by decomposition.
She told me that she prefers to get to the bottom of things, etc. I then asked her if all that effort would pay off. It doesn't, because People Do Not change. If a person has the habit of going behind another's back, breaks protocol in work ethics ; what could we possibly hope that this person would improve on? Behaviour is never easy to alter, because a lot of it is instinctive. It's tendencies that cause people to do what they do, more often than not.
Most people REACT.
So, between friends, I could accept a few back-stabbing oversights, say 2 slashes. After that, don't you think my survival instincts would kick in and tell me to find a marker and redraw the lines? It's cleaner and it cuts out my stress level.
If the other party doesn't value the relationship, be it a business or friendly relationship, then it would be better to find another party who is keen to at least observe the very basics in ethical behaviour.
So, if a limb is rotten and giving you trouble, go ahead, chop it off.
It would save you a lot on painkillers, migraine and money.