Omar Currie wanted to spread a message of tolerance and received a return message of extreme intolerance back.

Dangerous literature. (via Wikipedia)

When a little boy ran crying to speak with his teacher, Omar Currie, it was because a classmate had called him gay. Mr. Currie's response was to gather the class together and read them a book loaned to him by assistant principal Meg Goodhand. The book was one Currie was familiar with, as he'd learned about it during an education course that shared strategies for talking about tough topics like diversity and tolerance in the classroom.

King and King is the story of two princes who fall in love and eventually marry. It's a children's book, so there's no graphic descriptions of sex or anything. Just two men falling in love and ruling a kingdom! It sounds confusing from a political perspective, but not a romantic one. Currie told The New York Times:

Sources: New York Times | h/t Jezebel