I'm so glad this got picked up.
@Tearsex
Before the Internet, monster girls weren't hypersexualized. They were considered monsters, but women (e.g., Lilith in Abrahamic religions).
Look at the soldier's uniform, it's clearly not a contemporary uniform so we can assume he is from a time before the Internet. We can also assume that he's not from a demonic cabal, so he wouldn't consider the figure of a demoness to be sexually stimulating.
The MC is from a time where girls with horns and bat wings are characters in a lot of movies, manga, anime, video games, et cetera. He would consider them to be more 'normal' than an average person from the 1950s.