Considering that the success or failure of abstinence is ENTIRELY dependent on human nature, you cannot separate the two. I refute the naive notion that abstinence succeeds every time it's tried. There are of course instances in which abstinence is just thrown to the wind and not even attempted, but I'm not speaking of those.
Good people fail. Good people fall short. It's a fact of life. Many times, with young people especially, the will to abstain is present, but the flesh is weak. To think that just because a young man or woman attempts abstinence that success is guaranteed, is naive at best. As it has always been the way since the dawn of history, a certain number of young men and women with the best of intentions will still be finding themselves asking, "What was I thinking?" the morning after.
You most certainly CAN separate the two. EVERY time abstinence is utilized, it is 100% effective. How can you connect failure of abstinence to the lack of use of it? Your logic is a bit warped.
But, as I say, if you have an agenda which includes the idea that young persons are just little monkeys who have absolutely no self-control and that there's no sense in expecting it from them, it would be to your advantage to twist the logic to suit.
Abstinence works--abstaining from sex will prevent pregnancy. Period.
Contraception sometimes fails--even when you use it there is a failure rate for all forms, including sterilization.
Your argument that abstinence fails when it is NOT practiced is like saying the condom failed because you forgot to put it on!
Attempted abstinence=attempted contraception. Both may fail.
Abstinence does not equal contraception. Only one may fail.
We are not animals--along with teaching abstinence is teaching not to place oneself in a position to lose all self control. If you are placing yourself in such a position, you are predetermining the outcome. This is like telling your child that they can hang out in a crack house and expecting them not to do crack.