While condoms are of great help in preventing the spread of AIDS, they are not 100% certain to work, which can produce behaviors that are the root cause of the AIDS crisis (moral hazards). We now have epidemics of STDs that wasn't as present in the past, in part due to a liberated attitude that came about as a result of birth control. I believe the Catholic Church says, first and foremost, that sex needs to be in a loving relationship between two people, as part of a larger relationship that covers all. Things needed for the preservation of this relationship are more than sex. What we have now is a recreational attitude toward sex, where people do one night stands, and a lot of suffering about. In this, is a LOT of STDs.
What can see here is a more pragmatic attitude towards the use of birth control. A need to emphasize what is idea doesn't have to mean that you don't accomodate for the less than ideal, if the lack of accomodating makes a crisis situation far worse.
