I suggest people read Benedict XVI's Letter to Bishops on the Pastoral Care of Homosexual Persons (written when he was Prefect of the Congregation for the Doctrine of the Faith).
It accurately reflects the Catholic moral dogma on homosexuality. While it clearly defines the phenomenon as unnatural, willful and gravely disordered as a psychological attitude, it is not in and of itself a sin. It's PRACTICE, though, is a mortal sin (one that put's one's salvation in jeorpardy).
Various Christian sects realize that it has always been an endemic moral plague on the human condition, with vast and disintegrating societal implications. It should be treated, however, with compassion for the afflicted and a realization that its victims need support as well as a healthy dose of reality on a topic that has been obfuscated by maudlin sentiment and lies.
What the Church objects to the most is the modern, post moral ideology that attempts to normalize, institutionalize and sacralize something that will always be deeply injurious to human life and destiny.
It becomes especially corrosive when it is imposed on young people whose moral attitudes and consciences are still in development, as an expression of 'love' which is harmless and inevitable, when it will produce only misery, isolation and disease. That said, anyone who assaults or slanders someone else for homosexuality is himself committing a sin.
Letter to the Bishops of the Catholic Church on the Pastoral Care of Homosexual Persons