This is a Westernized interpretation of the concept of "Left Hand Path". In the Eastern traditions, it's mostly understood to mean "unorthodox" or "unbound by tradition", something like that.
As I'm sure you can imagine, this misunderstanding would be like if we all agreed that posting frog pictures is "evil" because DHS told us to stop posting evil white supremacist photos. All of us equally understand those two things are not related.
In just the same way, everyone who is apart of those traditions would just look at you like you're retarded if you said that someone who doesn't follow any organized religion is "evil". They would probably even kick you out of the city when you started calling them Satan and telling people they're possessed by demons.
I understand the allure of framing things this way, but you're going to deplete people's attention to the subject by jumping right to the final categorization each time. This is why people ignore teenagers when they tell everyone their life is "the worst ever".