(Part 1 of 2)
Fr. John Baptist Ku OP teaches at the Dominican House of Studies in Washington, DC. He recently finished his PhD in Systematic Theology from the University of Fribourg, Switzerland.
This talk on Paul VI's Humanae Vitae (On Human Life), which looks at the moral teaching of the Church on contraception, was given to the friars in formation a few years back. It is very important to see that the preaching of the Gospel also must include those teachings of the Church that are not always popular.
That being said, the way that difficult teachings of the Church are presented is very important so that God's people can see the Truth and move towards it, even desiring it for themselves. The Dominican works diligently in helping others see this Truth, who ultimately is Jesus Christ! In the preparation for such preaching/teaching, the Dominican dedicates himself to prayer & study for the sake of the Gospel and the salvation of souls.
(Part 2 of 2)
I would also suggest that you check out a famous talk by Dr. Janet Smith: "Contraception Why Not?" I gave this CD to all the couples I would prepare for marriage when I was working in a parish.