One of the most interesting facts I find about people today is they don't use common sense. We all know that orange juice is good for you, it has vitamin C. But orange juice consumed by the gallon daily is NOT GOOD for you. So if someone consumes a gallon of orange juice everyday and becomes diabetic, does this imply that orange juice is evil and has no merits? Overdoing anything, even the best nutrient, and you can overdose.
As a Chinese, and still eating Chinese food 90% of the time, no one in our family overdoses on soy. We drink 16 oz of soymilk at the most per day. Fresh soybeans (edamame), only a handful twice a week. Fresh tofu, freshly fried tofu, miso, tempeh, real fermented soy sauce, fermented soybean pastes, are consumed in larger quantities. But we never eat soy alone. And we don't have these strange soy hotdogs, soy burgers, soy powders, soy shakes, engineered soy products.
Babies are never fed soymilk. As soon as babies can start eating food, they are fed fresh silken tofu, as it is an easily digested protein. But tofu is never the only source of protein. Small amounts of ground meat, milk and regular food are fed to babies.
As for adults, tofu will always be eaten with eggs, or meat or fish in a meal. Never by itself. The same with soybeans, miso and soy sprouts and soy sauce, etc.
I believe that Chinese and Japanese have eaten this way for centuries. And because we consume mostly tofu and fermented soy products, you don't hear people having these kinds of problems. Soybeans are naturally high in trypsin. The process of fermentation and tofu making is what deactivates trypsin, and makes it safe for consumption. That is why soymilk and edamame are not eaten in large quantities.
Also what is unknown to most people is that Chinese eat larger quantities of soy bean sprouts and black soy beans. The black soy beans are commonly mistaken as "black beans", but they are not the Mexican or South American black beans. Black soybeans have higher protein content, and are considered superioer to yellow soybeans.
Even though soybean sprouts have phytoestrogens, they contain less phytoestrogens than alfalfa sprouts. One birth control pill has 5000 times as much estrogen as 20 grams of soy sprouts. So eating soy sprouts occasionally (as in once or twice a week) does not hurt you. But going overboard and eating large quantities everyday is not good for you.
And until Americans started producing soybean oil, the majority of Chinese was raised on peanut oil and safflower oil (made by pressing you choy).
The first written record of the soybean plant is contained in the book "Ben Ts'ao Kang Mu", describing the plants of China by Emperor Shen Nung in 2838 BC. They have been cultivated and eaten since then.
If a food has been eaten for 4800 years, I'm pretty sure there is enough empirical data to show that soy itself is not evil. If the plant was toxic in any way, it would be listed as such in the "Ben Ts'ao Kang Mu" and the Chinese Materia Medica. Perhaps engineered soy foods, such as soy hot dogs, soy protein powders, and such should be eaten sparingly.
But if you have any doubts about soy, you shouldn't eat too much of it, and definitely do not eat engineered foods. As in everything, moderation is key to good health.