Following that, we would have to isolate and destroy the stupid gene that produces all leftist inclinations.
The one silver lining to leftists is that they're self-terminating. Leftists seek comfort on the government's teat. They want other people to do their work. When those "other people" are traveling among the stars and the leftists, seeking comfort in what they know, stay behind on Earth, eventually this society will fall to apathy and sloth while those among the stars survive and thrive.