If you call yourself an atheist, but you believe that an alien seeded life on Earth, you are not an atheist, you just have a weird concept of the nature of God.
Hitler thought he was improving humankind by killing disabled, mentally ill, poor, and otherwise "inferior" people. Ironically, interacting with such people improves humankind as it teaches individuals compassion, patience, humility, charity, and dozens of other Christlike qualities.
One of the theories about the creation of the first cell on Earth is that lightning or some other form of energy created life out of inorganic matter. Makes sense to me since Genesis 2:7 tells us that "the Lord God formed man of the dust of the ground." Why wouldn't God play by the rules of the universe?