It's a horror version, of course there will be "evil" symbols on the nightmare demonic entities and one who creates curses would be ideal for the inverted cross - curses are basically the opposite of praying and blessing and an affront to God so it's an appropriate use. They are also staple horror aspects in media and this is extremely tame and tastefully done, overall this is probably some of the most PG-13 horror in games that I've seen to be honest, no anxiety inducing jump scares, no time pressures and every aspect of the game encourages paying full attention to what you read and tiny details, those make this ideal for older kids and teens, especially when they need to be able to pay attention to detail in their studies and a lot of media doesn't demand much attention at all. Nacho has worked their butt off on this game making sure that some disabilities and phobias are taken care of and having it in different languages (3 at time of comment) to try to include as many people as possible but they can't cater to the whims of every single individual, Let's say for example I was big into paganism and I'd personally like more representation to pentagrams as a religious symbol on one of the more classical demonic looking entities so if they took both opinions at the same time and swapped the inverted crosses here for basic earrings and the earrings of the witch for pentagrams then that would offend someone but for many those are a religious symbol so removing them would then offend someone else who would then want something changing and their change may offend someone else etc - see how that just wouldn't work out on such a large scale with everyone wanting different tweaks based on their own beliefs and feelings? It's a balancing act and so far they're doing a great job :)
They've gone above and beyond for their players so far especially as an an indie dev but not liking a pair of earrings isn't going to be the same priority in development as providing access for different languages, disabilities or making sure phobias aren't triggered by gameplay. Maybe down the line they can release a version stripped of things like this as a menu option but this isn't what the vast majority want for the main game and it doesn't have the same urgency as things like making the game in more languages or providing a version with larger text and images for the visually impaired or keyboard control for those with disabilities that can't use a mouse etc. The reason those take priority is while you can play classic and story mode to avoid the nightmare level's dilemma they can't play any part of the game at all so that needs to be taken care of first. We're very early days in terms of the game but from what I've seen Nacho really listens to feedback, maybe this will be an option once other things are taken care of.