The credibility of this commentary rather severely crashes with this statement. The original studies linking breast cancer were made long before the pro-life movement had any knowledge of the results. The implication here is almost that the studies were sponsored by pro-lifers looking for a result.
The author also shows a minimal grasp of logic when using the stated lack of differentiation in the studies between induced and spontaneous abortion as somehow discrediting a finding that induced abortion itself ups the risk.
The problem is really that statistics can be spun any way you like. If you look at the entire population of women as a whole, it is probably more accurate to say that childbirth reduces the risk of breast cancer, since women who have had abortions, women who have miscarried, AND women who never were pregnant are all more likely to get breast cancer later on than women who bore children. Unless we want to stigmatize all childless women, it is probably not the best idea to go around saying they will get breast cancer due to their lack of offspring.
There are so many angles to this debate that are worth exploring; unfortunately, an opinion column is limited to 600-700 words. That's why I prefer live debate--you can get to every point more quickly.