I think all of you are going in a wrong direction in a crucial point. Not allowing something cause it's inappropriate is not equal to censorship. Not allowing something in a domain where one is the one who calls the shots isn't censorship. If he forbade him to recite or share his poems outside from class, THAT would be censorship. The freedom of speech gives you the right to say or write everything you want, but not everywhere you want. You still gotta obey to authorityfigures in their domains. As cursing and cussing is forbidden in schools, I think it's OPs right as a teacher to decide what he want's to work with. I bet you people would be losing your shit if the poems were homophobic or racist or anything. But maybe for OP these poems of demons weren't any better. Maybe they were bothering him. Maybe they were affecting his life, giving him nightmares. Who are you people for trying to blame OP for trying to make his workplace pleasant for him?

1. That is offensive to Spn fans 2. He's being creative not mass murdering everyone

I mean it might be different, but it's not harming anyone just scaring them it's called creative writing for a reason I really don't see the problem here they are many worse things in life or hell on Tumblr then some persons demon stories

That's what happens when you try and stifle creativity, OP!