Click this link to view his letter: Fr. Welzbacher Letter about Humanae Vitae .
This is the concluding paragraph of Fr. Welzbacher's letter.
" "By their fruits you shall know them." The fruits of the contraceptive revolution point persuasively to the conclusion that Pope Paul the Sixth was right and the world was wrong when he warned in Humanae Vitae that evil is evil and will bring forth further evil, which forty years later is what has come to pass. "