When I was in 4th grade CCD class ("CCD class": catechism class for little ones - to teach the basics of the faith, if you don't attend a Catholic school), my volunteer teacher was trying to show us how to pray the Rosary. The Rosary is one of the most basic, fundamental of Catholic prayers. EVERYONE - even non-Catholics - at least recognizes a Rosary, even if you don't know how to pray it.
As the teacher started the lesson, I got puzzled. I raised my hand: "That's not right.". My teacher, in a sigh of relief, said, "Do you know how? Here, show us" and I did. I was 9 years old.
Why do I share this? Because it illustrates the problem of Catholic catechesis: we have several generations of Catholics who just don't know their Faith. How sad.
The problem, though, isn't that 30 year olds don't know how to pray the Rosary (although that's a problem); it's that a majority of Catholics use contraception, and don't really have any idea why. It's just a cultural thing: you have 2.3 kids and that's it. They don't understand why the Church teaches what it does about contraception, or that it is part and parcel of an entire, universal and complete understanding of human sexuality and God's hope and promise for us. They have some false notion that the Church (in her stodgy-can't-keep-up-with-the-times-busy-body-in-the-bedroom way) wants everyone to pop out as many babies as humanly possible, with mom perpetually barefoot, pregnant, nursing and happily humming while folding diapers.
Even worse, those who aren't Catholic can't figure out why this is a BIG DEAL. They have never take the time to truly engage Church teaching, and look at what we Catholics are called to live.
Look, I'm not gonna go over the Church's entire teaching about sexuality, procreation and birth control here. If you wanna debate about, at least do us the favor of learning what the Church ACTUALLY teaches. Read Humanae Vitae (that's Pope Paul VI foundational teaching on birth control). Read the Catechism of the Catholic Church (especially para. 2370 and on).
After 9/11, many people took the time to read the Qu'ran, to talk with American Muslims who were grounded in the faith, and to educate themselves about Islam.
If you disagree with the Church on contraception, or just can't figure out what the big deal is, ask yourself: "Do I even know what I'm talking about? Do I have even the smallest clue as to what the Catholic Church actually teaches in this regard?" If you believe yourself to be under-educated, then maybe it would behoove you to learn.