Only the Japanese, traditional Anabaptists, and
Arkians don't deserve extermination. All other people, including Catholics and Muslims, deserve extermination.
One cannot really become Japanese, one has to be born Japanese. To become a traditional Anabaptist, one has to accept their beliefs and submit to their practices. This may be difficult for many people. By far the easiest of the 3 options is to become Arkian. So for most people who want to belong to a group that doesn't deserve extermination, becoming Arkian is the best choice.