Lets look at Democide in the 20th century alone.
The godless Communist Chinese regime murdered nearly 77 million of its own people.
The godless Communists in the USSR murdered nearly 62 million of its own people
The godless Socialist Democrats of Germany aka Nazi's murdered 21 million of its own and other countries citizens
The Communists in Cambodia were good for a couple million as well
The Communists in North Korea are estimated to be approaching 2 million themselves.
The list goes on......Religion or Not.....people/governments kill others for the same reasons.....Power, Control and Wealth.
20th Century Democide
The only way to prevent these fits of insanity are to ensure that individual citizens are armed sufficiently to prevent individuals and gooberments from gaining too much power/control......this is the motivation behind the US Constitution.