Er, Nazism was not securalist - have a look at Mein Kampf and see how many references to 'God' or 'Divine Will' you can find. As to Communism, you need to establish cause between secularism and the communist abuses.
In a way, I agree with you, concentrating on Religious abuses is inaccurate - however, in my opinion, the real danger is
Ideology of any kind. Anywhere Ideology replaces rational thought the outcome will be sub-optimal at best and harmful at worst.