I've found that culling for quality in your flock also works wonders in the human world. I guess you could even say it works great on this thread...those who get their feathers ruffled and attack the advice given are soon discouraged that the advice and the tone thereof never really changes here. They put up a fuss, get all feisty but they soon leave the thread/barnyard seeking a flock that has the same goals they have.
We don't give in to guilt, declarations of how we are all just jerks and lack any sensitivity to newbies, etc. We just maintain a constant, dependable thread of practical information. We maintain a steady, healthy and tough strain of info that isn't derailed by momentary changes in the quality of the birds introduced from outside sources....it's not that the flock must be all the same breed, color, size or other surface quality. It's that the goal of this particular flock is to produce a strong, self sustaining, productive flock that takes little maintenance to maintain healthy productivity. One really can't do that if every delicate bird has to be nursed along until, if ever, they are strong enough to be with the rest of the flock, standing strong and tough.
It's the same in your flock...a person needs to find a husbandry method that is solid and works where they live and with the type of chickens/breed/goal they have. If you are strongly consistent with those goals, eventually the chickens that simply aren't going to work toward that goal will evidence themselves by their differences....any weakness, any difference in quality of feathering, productivity or overall health with soon stand out when comparing it to the fine qualities in the rest of the flock. Over the years it gets easier to recognize the birds that don't have the qualities you seek because you have dealt with so many that have...it's easy to recognize the counterfeit if you have studied the real thing over and over.
I guess the thing to do with chickens and in life is find out what kind of flock you want and then work diligently to make it happen, sentiment aside and with single minded determination. In life it applies to so many things....the kind of peace you want, the kind of people you surround yourself with, the kind of family you want, the kind of job you want. It all depends so much on what makes your life complete and how willing you are to focus on the good qualities while consistently weeding out the less desirable like stress, anxiety, feeling overwhelmed, feeling like those around you drag you down, etc.
If a single bird causes turmoil in the flock, it's best to just remove the single bird instead of approaching it like a flock problem. Roosters are a prime example, as are birds that are picked upon, etc. Raising chickens is so much more enjoyable if you keep your eye on the goal and pursue it....if only life could be as easy as maintaining a good flock of chickens!