Yeah I agree, but would also add that we don't have to "match" the entity's frequency for them to possess us. These entities are attracted to vulnerable emotional states, like someone going through addiction, grief, insecurity, arrogance, altered mental states induced by drugs, etc. There are some theories that these entities live in an alternate dimension and that we kind of "light up" in this other dimension whenever we are in a certain emotional state. They are attracted to it, and whenever someone is in one of these states we are like a beacon for these entities. They smell blood in the water and attach themselves to you. Once they attach, they manipulate you to engage in more and more of these behaviors that are ultimately self-destructive, because these entities feed off something we give off when we engage in these behaviors and experience these emotional states. Over time we become more and more evil. So it's not that we have to emulate evil in order for them to attach, it's that they attach when we are vulnerable and manipulate us to emulate evil behaviors more and more over time. Once the process is complete, it is referred to as "perfect possession", meaning the possession is complete and all encompassing and basically impossible to undo.

It's very interesting to think about. There are stories of people who sensitive to being able to see evil, and they will walk into a casino and see the degenerate gamblers at the slot machines and actually claim that they can see various monstrous creatures attached to these people. Puts a new perspective on the whole "monkey on your back" thing. Or think to the movie Shutter Island when Leo DiCaprio's character said that his wife who killed their children claimed that there was a spider in her brain pulling the strings and making her think and do certain things.