Communists (atheists) done a lot more harm than any religion, and they hate gay marriage too. Anything powerful can be used to do a good thing and a bad thing. Any institution can be used to do an evil thing, neglect, or be corrupt, e.g. police (police can be abused to protect corrupt regimes), courts or event justice as whole (slaves were legal in many countries), church, etc.
Communists is not equal to atheists , in fact most of the atheists I know are not communists. Blaming to atheists the crimes committed in name of communism is like saying that as Hitler admired christianism all his crimes should be blamed on christians . And right the ones trying to impose their beliefs, and deny rights to others, in Europe and USA are the followers of some of the Abrahamic religions.
That line of thinking is dangerous, you can assume that televangelists are scammers because they are christians or that priests that abuse children are abusers because they are christians. and not, they are because they are bad people. Stalin/Mao/etc .. were bad people and that's the reason they did what they did not because they were atheists or communists, when a priest abuses a child does it's because he's a bad person not because he's a christian.
