I think you tend to misrepresent Robertson's and Falwell's words and intentions a little here, (and I'm a Catholic, no apologist for evangelicals and fundamentalists).
I think the premise for this "Falwell/Robertson line", as you call it, is not so much that the Islamofacists slammed their planes into the WTC buildings because God told them to punish us for abortion, but that men exist who wish us harm, and perhaps God won't be so protective of a nation that sends His children back to Him faster than He creates them. That's the connection I believe Robertson and Falwell were trying to establish between abortion and 9-11.
It's not a difficult proposition to understand, really, and I think this secularist attack against people like Falwell, Robertson, the Pope, etc, by placing distorted interpretations to their admonitions is part of our problem in America today. Everyone wants to be their own moral theologian, ignoring the Bible, and Christian teachers who may be more gifted in that department, and who just might be saying something worth considering and investigating before condeming.
Hear! Hear! (or is that Here! Here!)
Here's the quote "The ACLU has got to take a lot of blame for this. And I know I'll hear from them for this, but throwing God...successfully with the help of the federal court system...throwing God out of the public square, out of the schools, the abortionists have got to bear some burden for this because God will not be mocked and when we destroy 40 million little innocent babies, we make God mad...I really believe that the pagans and the abortionists and the feminists and the gays and the lesbians who are actively trying to make that an alternative lifestyle, the ACLU, People for the American Way, all of them who try to secularize America...I point the thing in their face and say you helped this happen."
The quote sounds quite different from your interpretation, IMHO, I'm not sure that mine is the one that is distorted.