I have been a practicing 'Satanist' for a very long time - on a spiritual level, 'Satan and his demons' merely show you your self that you would rather not admit to (like sulphurcrest pointed out and called your 'shadow'). The evil you feel within and see within others are simply the faults and insecurities that tear you apart inside and the faults and insecurities you experience from others because you cannot deal with your own inner demons. This doesn't make you weak, it just makes you empathic, or at least more aware, towards all the baggage that us humans share. It is nothing to fear, it is actually a very beautiful gift if you know how to filter and work with the fear and compassion.
I do not work with Satan or any of the demonic hierarchy as literal demons, as I also try to stay away from the dualistic idealism of the Monotheistic faiths; I understand 'Satan' and the Qliphothic hierarchy as shadow selves of violence, terror, and insecurity that must be dealt with. If you look closely at the story of Lilith, you will see she is not some evil blood sucking, children killing bitch, but the First Lady of Adam that was forsook simply because she wanted to take control of an intimate situation and be as an equal to Adam (as so-called Satan, as I interpret to be Semyaza, wanted to be an equal to God).
And finally, if any being comes to you and demands that you worship them it is one of a few things, two of which are the most obvious to me - your mind stuck in fear getting in your own way (which is most likely) or a trickster spirit trying to confuse you and lead you on a path of self-destruction.