Of course this poem is influenced by some sexuality. It doesn't mean it's bad. Try to focus on his creativity,imagination and composition in the poem.One of the ancient philosopher, Freud said that people's attitude and behaviour are influienced by the sexuality all over his life. Sexuality is a major part of human mind and body. Although every person doesn't express the sexuality verbally, they are  constantly expressing it in different ways. Like a boy who hates to talk about sex might look at the beautiful girl walking on the parking lot.

May be this poem is just a another way to express his sexuality in an artistic form. Not bad at all.So, don't harrass him for his poem.If you look something with open mind and positive attitude, you will always get something new idea and concept. Just my personal opinion.