I think he's referring to the isoflavones in soybeans which mimic estrogen and are possibly linked to multiple hormone-related health issues.
While everything you eat affects your body in some way or another, consuming isoflavones in sufficient quantities which convert into phytoestrogensis a bad idea as hormone balance is especially sensitive to such consumption... well... for men anyway. For post-menopausal women, there have been beneficial effects in studies that show it's similar to taking low-dose hormone-replacement therapies -- ie estrogen pills. There's also a theory that increased soy products have aided in increased breast sizes, early puberty, and low sperm counts... though it's far from proven.
The National Institute of Health states results from various studies are mixed and that it supports further study, yet cautions women who are at high risk of breast or cervical cancer from eating lots of soy.