I usually get weenie filter tagged on threads like these ...
Switching form RL to d&d is of course a problem.
If you over simplify Satanism as the polar opposite of Christianity,
and ignore the difficulty of translating C or S into D&D (mentioned again)
...
Taking C at face value, C says there is no good outside of God.
When you do good, you're only doing it because God is doing through you.
All other gods (lower case G) are not good.
Their worshipers only do Good because it's part of Gods plan.
Perhaps the same could be said of those gods, doing Good only because ...
So none of the other gods are actually Good.
Now flip that over for the S position.
So fluff can go a whole bunch of ways at this point. Crunch too.
I'm not trying to suggest a full RL/D&D translation,
or a fully accurate translation, of either.
but take it with a grain of salt.