Word Smith: Cull
The verb “to cull” means to select or gather.
Example: “If you decide to make a literary anthology, you must cull the best possible stories and then arrange them in a pleasing manner.”
When you use cull as a verb, the things you gather can be the good or bad ones from a group. In your garden, you can cull both the good vegetables for dinner, as well as the rotten ones for the compost pile. In fact, often no judgment of quality is made, as when you cull information from the Internet for your next research project. The sorting through will come later.
However, if you use the word as a noun, a cull is a selection of things you intend to reject, often in reference to a group of animals. For example, suppose there were an outbreak of a disease such as foot-and-mouth disease on a farm. In that case the governmental authorities can order the farmer to perform a cull of farm pigs. Removing the unwanted and diseased ones and killing them.
Culling is intended to protect the larger universe of animals and plants. It is destructive, but it is deemed critical to the survival of others in the species. So culling gets to the idea of greater good. “I will kill this ONE because it is better for EVERY OTHER in the population if the one is not around.”
The measles outbreak has the feeling of a cull. We will vaccinate everyone for the good of the rest of society.