What you're describing is called dogmatic thinking and it's not solely the purview of religious thinkers.
I know a number of people who are pushing dogmatic view points as atheists, as democrats, as republicans, as just standard people.
I mean, even what you're asserting here is a dogmatic viewpoint of the many new gen atheists. There's no study or proof that shows that religious thinkers don't think about morality the same way that secular thinkers think about morality or that religious thinkers are any more dogmatic than their secular counterparts.
People have a tendency to do awful shit when they think they're not being watched. You're just describing the average person.