One of potential love interests is Damien Lavey (tribute to the founder of the "Church" of Satan), who is "son" of two "Kings of Hell". Another demon, Dahlia Aquino is named after Michael Aquino, founder of Temple of Set, another branch of satanism. I am sad that GOG offers game, which de facto promote satanism. There is also a witch, which wears reversed cross. Maybe I am hypocrite, because I play another games, where demons and satanism is depicted, but at least in most games they are not depicted in friendly and symphatetic way.

I find it quite strange that from the names of a few characters likely referring to some religion to the conclusion that you conclude that the game "de facto promote"s that religion. Would you care to explain how that works? From your last statement it seems that you specifically have a problem with the fact that those characters are friendly/sympathetic. Why is that a problem? Is it just because it is not the religion you adhere to?

"Is it just because it is not the religion you adhere to?"
It is because it's religion, which is blasphemous opposite to my religion. Relation between christianity and satanism is "special" - if You promote one, You de facto fight with another.
And yes, I think that depicting symphatetic characters referring to some religion can be promoting that religion.

It's called "Monster Prom". What exactly were you expecting?