Oh no, not this again…
I will admit, I do have heartburn when the names of actual demons are mentioned in the game (some of the “statted, therefore you can kill them” villains are Asmodeus and Beelzebub, and in one issue of Dragon someone unofficially statted up Satan – that one was quickly forgotten and is an old shame for painfully obvious reasons – that does bug me, as real-life evil forces should not crop up in a game. But OTOH, DMs can easily ignore or exclude those names from the game.)
That doesn’t mean I think that having a villain summon demons and end up having his comeuppance come either at the claws of said demons or at the swords of adventurers putting an end to him is harmful to souls. I don’t like (and as a DM actively forbid) heroes or player characters from summoning demons, as it is not a heroic act or one to be emulated by players. But to say that its mere existence in a fantasy game is inherently Satanist is a bridge too far for me. It’s how it’s used.
I doubt that Satan inspired Gary Gygax to create D&D. It is, when played right, a good and wholesome activity. However, he can use careless players as tools.
Then again, he can use beer, which is good and beneficial and a sign that God loves us very much, to turn careless drinkers into alcoholics. Or sex, which in the form intended by God is a live giving act, into a selfish and narcissistic and mortally sinful behavior. Or food, necessary to life, can easily become gluttony. None of those things are evil in and of themselves. Everything is good and is blessed by God. It is how it is used or abused that turns it sinful and evil. And it is that potential that the Devil corrupts with.
All of that being said, if Holy Mother Church were to exercise her ordinary magesterium and explicitly tell us that D&D or other RPGs were sinful, I would stop playing them out of obedience. But no such pronouncement has been made as far as I know.