I grew up unaware of my culture or sexuality because I did see myself in books, I was an avid reader living in a white world. I believed, incorrectly, that I was white and that I was straight. Once I found stories and people that made me aware of the person I was, I didn’t feel lost anymore. Many students are in a similar situation or worse and diverse stories are life saving for some. I understand that many people differ in opinions, and not all stories are for young children, but students can handle explicit stories (otherwise why would we read Shakespeare stories). Children's books with gay parents are NOT harmful, novels of black and brown characters are NOT dangerous, and limiting students as though those are bad teaches kids that they are morally repugnant. 
Lastly, if you don’t like it, don’t read it. It is distasteful and poor judgement with negative consequences to ban books on the grounds of discomfort.