How about the correlation between diet and breast cancer? Asian women (in Asia) who ate a typically low fat Asian diet (lots of vegetables, rice, little meat, no frying in fats) had very low rates of breast cancer. With the introduction of Western foods, rates have dramatically increased.
Maybe there was more breast cancer in the past that remained undiagnosed. Maybe it would have developed in a certain percentage of women anyway had they lived longer, much like prostate cancer showing up because men are living longer.
My gut feeling is that it correlates to birth control pills (particularly the higher doses given years ago), perhaps in conjunction with smoking or secondhand smoke.
The author picked seven factors to study. Diet wasn't one of them. He then concluded that abortion was the strongest predictor, and from there that the relationship is causal. A dramatic leap without the kind of literature review and discussion one would expect before drawing such a conclusion.
Actually, I am not sure this accurately describes the work. The author sounds convinced he has a causal relationship from the get-go.
I realize that many people may want to believe that abortion is a cause of breast cancer (which it may or may not be). But it is better to rely on high-quality research. The lack of objectivity here is too evident.