"human? pfftt humans are so over"
Posthumans are snotty elitists who think humans (and even most transhumans) are so over. This entails forcibly rounding up all humans and violently destroying them all. Until they can accomplish their goals, hunting the final holdouts to meet a slow, grisly fate, and even all human beings in earlier time periods (which would create a Paradox), they cannot feel truly posthuman themselves.