You know, it's interesting. My biggest opposition doesn't come from the kids. When they hear me talk about abstinence, they realize at once that it's a matter of being practical: Do I really want to get a disease? Do I really want to get pregnant? But adults often think I'm criticizing their morality. Many of them grew up during the sexual revolution, so when they talk to their children they say, "Sex is beautiful; but be careful out there."
It's a very mixed message. Sex isn't evil. Sex is wonderful, and we should teach our children to respect it. But under what conditions is sex wonderful? People engaging in premarital sex usually report that it is not wonderful.
I think we have to model the message. Is everyone going to wait until marriage? No. But that doesn't mean we shouldn't set a standard. I'm certainly glad I did.
I would add that this generation are casualties of the sexual revolution -- every revolution has casualties. Because they were given no standards or boundaries in sexuality they are an amoral (not having any moral standard) generation, therefore viewing sex as pragmatic. Boomers, however, grew up in a time where the cultural standard was to wait until you were married. If you did have sex at least you were discrete about it, they consciously rebelled against the cultural standard/morality. Thus they view any retreat in premarital sexual activity as the imposition of morality on themselves.