The Church’s teaching on homosexuality and marriage is Catholic because it is true, not true because it is Catholic.
In other words, the conclusion that same-sex relationships should not be afforded legal status is because it is based on the truth, not just on Catholic teaching. Yet, saying that makes this conclusion all the more controversial.
If it were based simply on Catholic teaching, opponents could say “You Catholics are entitled to your opinion, but that is not binding on others.” Instead, saying that** truth **is the reason that same-sex relationships should not be afforded legal status is offensive to those who deny the existence of truth, who prefer to live in a world dominated by what Pope Benedict XVI termed a “dictatorship of relativism.”
If you acknowledge that truth exists, then we can discuss and even argue about whether or not I or the Catholic Church correctly understands the truth of this matter. But if you deny that there is such a thing as truth, that is, the truth, not just my truth and your truth, then the matter becomes merely an exercise of raw political power in terms of who has more votes to impose an agenda, and that is what makes it ultimately tyrannical.