I'll skip the statsbattle (suffice to say if you actually carefully practice NFP it has a 98.7%  effectiveness rate of avoiding pregnancy), the utter stupidity of the claim people who aren't directly experiencing something in their lives can't assert truth about such realities, and just go to the heart of the issue. 

I'm married. My wife and I are 30 and 29 yrs old respectively. Our physical attraction to one another is just as strong as it was when we were dating/newlyweds. Everyone who is married knows that marriage does not equal the constant satisfaction of all sexual desires for both parties at all times. Our selfishness/egoism, antithetical to the Gospel of Jesus Christ, is often times exquisitely demonstrated in our sexual relationships. Contraception is particularly insidious because it is a mutually agreed upon selfishness, a real "You get yours and I'll get mine and we'll be happy together" scenario. It's an avoidance of surrender to God and the natural order of love.