>>853294
Humans are weak. What this means is humans can commit acts that favour Satan over God but, once their mind and feelings have changed, come to see that the evil in their choices and feel regret. Humans don't necessarily mean what they do, basically and a huge part of this is not being able to always see the fullest consequences of our actions at every moment due to weakness leaving us vulnerable to being blinded by our own emotions. A person's bad choice in a moment isn't necessarily reflective of whether they truly wish to eternally be with Satan.
A Satanist however has committed himself to Satan. It's true that even he might change his mind at some point but nonetheless, not only are they not making use of the opportunities God is giving them to repent but they, until converted, don't even want to.
Christians can make mistakes without leaving God behind entirely. Stumbling is actually an expected part of the journey.
The Satanist, unlike the Christian sinner, has explicitly rejected Christ. That's the difference.