Um, you forget, they made their place a 'sanctuary," and many were raped and slaughtered by some other bad people. Their mistake was trusting ANYONE not already in the group. Had they walled the place up, kept to themselves, not advertised they were there and not welcomed strangers, NONE of the Terminus story would have happened the way it did. You're talking about the difference between television and reality. In reality, you kill everyone you can, because everyone is a threat. If you go in with the "everyone is innocent until proven guilty" idea in that context, it's a quick slide down a short hill into the mouth of hell. Conversely, I'd kill anyone who tried to welcome me or my group in. For the same reasons. Steal their resources. Why POOL resources, when you can take them ALL for yourself?
Y'all don't understand, TWD is television. In human reality, things would be horrifyingly different. Just people would be horrifying. Go see the movie "Apocalypse Now," and watch the sampan scene.
The most important resource you can possibly have in a bad situation is people.
I've been through a disaster before, a 7.0 earthquake when I lived in California. We were without power and water for weeks, store shelves were empty for a while, and emergency personnel were far too busy pulling people out of collapsed buildings to be able to police us. You want to know how we behaved? The exact opposite of the way people behave in the movies during a disaster.
The vast majority of people were at their very best. Our whole neighborhood banded together and took care of each other, and we were not a tight-knit community before the quake. People who had surplus supplies shared them. A guy who had a generator let people use it to charge their batteries. He also brought a TV outside so that the whole neighborhood could watch the news, and we were all very surprised to discover that we were among the last people on earth to find out that the Berlin Wall had come down. We had been so cut off that we were completely unaware that a major historical event had taken place.
For the most part, people were calm and helpful. We would stand in long lines that stretched around the block waiting to be let into stores to buy supplies. People stood in line patiently and filed into the stores in an orderly manner. No one fought over the items on the shelves. Total strangers would share their stories with each other and help each other out. There were no police to be seen anywhere. We didn't need to be policed; we policed ourselves.
People were actually more friendly and generous during that time than they were before it happened, or afterwards once things returned to normal again. Of course, there was a small percentage of people who looted, but even during the best of times, there will be criminals. However, the overwhelming majority behaved in such a noble manner that it was surreal. The disaster brought out our "better angels".