Few biological forces are more powerful than sexual selection pressure, which is often used to explain everything from peacock feathers to human mid-life crises. What will be particularly interesting to see will be the second-generation effects of the boomers' sexual "liberation" as STDs run rampant through their kids, many of which can lead to sterility, either through biological damage or simple unattractiveness. So now we have the Roe effect putting pressure on leftist morality, and STDs effectively wiping out a generation of lascivious youth. Even if they don't die from their diseases, if they can't or won't reproduce then they're effectively dead biologically... except we're talking about memes here, so even the "dead" can spread their fatal philosophies on to others for a while.
The biggest cultural advantage of Christian morality -- aside from being spiritually right -- is that it gives its hosts tremendous reproductive strength and children that are likely to pass on the meme. Competing leftist ideals lead to death.