It's worth noting that all Christian denominations uniformly condemned contraception use prior to the 20th century. But yes, now the Roman and some Orthodox Churches are virtually alone in prohibiting it.
The first half of sentence is obvious, as the Catholic church is basically alone in maintaining its stance against contraception now. But the second half is a naked assertion of your own religious dogma. Your (presumably Protestant) church may teach as much, but simply stating it doesn't make it so.
Again, this is the Protestant view, and is not representative of Christianity generally. All of the "high" churches hold that the sacraments convey special graces, which would make them much more than merely symbolic rituals.
Gonna try to bring all this back to the earlier discussion of objective moral truth and catholic dogma. Ready?
Seems to me there's a bit of confusion around here regarding the precise nature of Catholic dogma, doctrine, and the rules and statements of the Catholic Church in general. Unlike most American Protestant and Evangelical churches, the Roman Catholic Church very rarely makes a definitive theological or moral statement which would be binding on its adherents. It's much closer to a common-law system than most believe. Catholic teaching, known as a whole as doctrine, separates out roughly into these categories:
Dogma: Teachings or articles of faith considered infallible by the grace of the holy spirit. This is extremely limited to points of major theological importance. To be considered "Catholic", you are required to believe and obey dogmas. Examples include the Trinity or Purgatory. (exhaustive list, with Imprimatur:
Dogmas of the Catholic Church - Catholic Apologetics)
Canon Law (aka rules or teachings): formal rules, teachings, or positions promulgated by the church. These often include positions on moral issues but are not infallible and are open to change at any time should the Pope or a council of the bishops with the Pope's approval see fit. Catholics are still bound to obey Canon Law, but since the Church does not "guarantee" their truth, there's some leeway for conscientious objection, recognizing the fallibility of the human church.
Theological Opinion: A theologian's opinion on a specific subject, which the Church has not formally spoken on. Often, these will be picked up by larger sections of the church and taught alongside Canon Law. These have no force until recognized.
Every bit of Catholic Teaching starts as an opinion, much like a single ruling in common law. The prohibition of contraception has been officially and formally recognized and encoded in Canon Law, but not as a Dogma. Therefore, a Catholic who firmly believes after prayerful discernment that contraception is morally justified, ie the right thing to do, in his specific situation is not sinning. However, a true discernment of what is right includes admitting to oneself that the Church is far less prone to error than any individual, and an examination of one's true motives for attempting to rationalize the breach of canon law. This is a fundamentally different, more humble cognitive process than one that is made when considering whether to break a secular law.
