You could ask the same question toward well known atheist states in human history many of which practiced communism.
Where they rational in behavior when it came to forcing people with opposing political and religious views into gulags, re-education/slave labor camps and operating secret police forces?In addition to violently quelling calls for greater individual freedoms among their own populace.
I keep seeing this argued by both sides. The ugly truth is that in both cases (non-religious states and religious states and historically religion in general) has been used as a means to control a populace. For communist societies the communist leaders wanted complete control and didn't want religion to get in the way. On the flip side, religion has and is wildly used as a means to control a populace as well. Its simply the means in which they employ to achieve the same gains.