Blessed Pope John Paul II writes in The Gospel of Life (1995), no. 97:
It is an illusion to think that we can build a true culture of human life if we do not help the young to accept and experience sexuality and love and the whole of life according to their true meaning and in their close interconnection. Sexuality, which enriches the whole person, “manifests its inmost meaning in leading the person to the gift of self in love.” The trivialization of sexuality is among the principal factors which have led to contempt for new life. Only a true love is able to protect life. There can be no avoiding the duty to offer, especially to adolescents and young adults, an authentic education in sexuality and in love, an education which involves training in chastity as a virtue which fosters personal maturity and makes one capable of respecting the “spousal” meaning of the body.
It seems to me that equating homosexual relationships with marital ones is an example of the trivialization of sexuality, of disrespecting the “spousal” meaning of the body.