Abstinence-only sex education is good for something

No, it doesn't reduce the amount of adolescent sexual activity--it merely reduces the likelihood that teens who have sex will use condoms, and thus increases the prevalence of teens with sexually transmitted diseases. This is not merely useless, it's actually harmful and counter-productive, like the Office of National Drug Control Policy's anti-drug advertisements.

But empirical evidence is irrelevant to those who are pushing their programs due to religious fundamentalism. For such people, the fact that they not only don't work but have the opposite of the desired effects just means they need to be pushed harder.