Secularization can lead to better outcomes and that is rational. If you take away a motivating factor that some people have to do bad things, then you are likely to get better outcomes. Again, you have to go back to the previous point I made about how non belief cannot drive anything to do anything.
If you believe religion can drive people to do good, then you have to accept that it can drive people to do bad. Non belief cannot drive people to do anything good or bad. If some of the bad is caused by religion and you take that away, then you get less of the bad.
It was already made clear that you do not necessarily get less but get a different rational for the justification of the evil. Part of the job of religion is to cure people of the motivations that drive evil actions. One could say that evil is the will not to be cured. If religion can't cure that what will?
Your answer to the question as to what evil is was that evil is bad. That's no answer at all. The real question being discussed in this thread, in my opinion, is whether on balance religion creates more evil than it cures.
The notion of good and evil come into existence with language and thought, abstraction, thinking language makes possible. They do not exist. This is what the analogy of the Garden of Eden and our expulsion is all about. In the garden there was no Knowledge, the notion that classifications exist. Evil is an invention of the language of duality. As soon as you have evil as a concept you can apply it to children. Once you do that you cause them to hate themselves. Once they hate themselves they need to deny that pain. That pain is turned outward as evil acts.
The purpose of religion is to present the notion that you are loved even though you are evil so that you will forgive yourself and stop your self hate.
Some make it and some don't.
My opinion is that we might want to introduce psychotherapy into the mix.
Our self hate is deeply hidden and profoundly denied, by the religious and the non-religious.