The Five Nights At Freddy's original characters are no different than my opinion of other fan-based characters from various games. I have no mind to the characters and I, myself, don't even mind interacting with them if I'm approached. Spyro the Dragon, My Little Pony, Black Butler original characters, they're all fan bases just like Five Nights At Freddy's.
Some people like to derive influence from those shows or games to soon create their own characters. Even if they never do, they simply find enjoyment portraying that existing character. Then there are people who play those fan-based characters because they like the environment they exist in. It's many sides to what a person likes in a game or show. Thus, I could never bring myself to say it's not appropriate. It's a game, nothing more or less. There are no real-life symbols that needs to be questioned, no conspiracies, and no threat to young animals.
It's simply another game people enjoy or dislike for their reasons. Create the characters, draw them, avoid them, or debate why they do what they do. All and all, Five Nights At Freddy's original characters are just another added fan base that'll be here, short-term or not.