Indulge me for a moment if you will. Before you read the rest of this post, take a moment and think about why the Catholic Church stands up against contraception and says that it's wrong. Why they didn't change with the times like the Anglicans at Lambeth in the 1930's and every other Protestant denomination since. Why, in 1968, they didn't finally capitulate and admit that times have changed, and so should our views on contraception. Why, when the government tells us that our Catholic institutions must pay for contraception, the bishops reply not only that we will not, but we cannot.
Please, take a moment and think about it. For many of my savvy Catholic friends, you already know the answer, but it is something that I often forget, too.
For the answer, let's go back to the beginning, to the genesis of it all. If you really want to make me happy, grab a Bible so that you can open it up and read it. Yes, turn to Genesis. No, we are not going to discuss Onan even a little bit. To understand why Catholics do not allow contraception, you have to understand the genesis- "origin or mode of formation"- of the human race.
Because I know you all had your Bible sitting out and ready to go, and opened it up and read it, I will now only emphasize a few parts.
"Then God said, 'Let us make man in our image, after our likeness...' So God created man in his own image, in the image of God he created them; male and female he created them."
Marriage is the area where this image is most clearly reflected to the world. We see this as marriage between one man and one woman that is open to life. "[A] man leaves his father and mother and cleaves to his wife and they become one flesh." (Genesis 2:24) As Scott Hahn has been known to say, the "one flesh" part is so literal that nine months later you need to pick a name.
Not that everyone has to be married. Better not be, or the whole celibate priesthood/religious life thing would be a joke, and what about those that are single and for whatever reason can't be married, whether as a heterosexual who just can't find someone, or a homosexual or transgender person who can't be married; this does not make anyone that is not married or is unable to get married as less valuable. We are all made in the image of God. But marriage, as a special way that the image of God is reflected, is not something that we can just make up to be whatever we feel is best. I could paint a pretty picture of a log cabin, but if I told you that it was a picture of the Taj Mahal, I'd be a liar. When something is made in the specific image of something or Someone, we can't define it just any way. It has to actually reflect the thing it is an image of. We believe that marriage is a specific way because it reflects a specific truth.
Marriage, then, is far from being the effect of chance or the result of the blind evolution of natural forces. It is in reality the wise and provident institution of God the Creator, whose purpose was to effect in man His loving design. As a consequence, husband and wife, through the mutual gift of themselves, which is specific and exclusive to them alone, develop that union of two persons in which they perfect one another, cooperating with God in the generation and rearing of new lives. (Humanae Vitae, 8)That union of two persons, that leads to the generation of new life, reflects not only about the reality of God, but also of the reality of the relationship that He wishes to have with us. It is a mutual giving of self that leads to new life.
"We didn't pick this fight... but we're not going to run from it." The reason that Archbishop Dolan is so adamant about this is because it stands at the heart of who we are as humans, who we are as children of God, and Who He is that we have given our lives to.