I am not sure how many tree huggers fully understand the Republican Environmentalism of feral hog slaughtering, but the benefits are far reaching.
Estimates are that there are about 5 million domestic swine in the US and that they are a major contributor to greenhouse gases.
http://www.aphis.usda.gov/publications/wildlife_damage/content/printable_version/feral_swine.pdf
Plus, there are an additional 5 million or so feral hogs in the US and you know they are greenhouse gas producers as well. Killing feral hogs reduces greenhouse gases.
http://www.livescience.com/28560-feral-pigs-running-wild.html
Feral hogs are tough on indigenous wildlife and indigenous wildlife is necessary to help retain harmony in nature. They can reek havoc on ground nesting bird, herpetofauna, and many mammalian species. Since hogs disrupt and destroy said harmony, killing hogs is good for nature.
Kill and hog and save the planet.