It's a load of nonsense from what I can see. So far tests haven't shown that they lower testerone. They also haven't shown that they effect estrogen levels/activity or act in the same way as estrogen when taken in at a physiologically relevant level. Maybe if you ate 5 pounds of tofu a day it might, but nothing is good for you in those sort of doses. Basically if they do have effects you need to be intaking them in ridiculous levels. Soy milk tastes like shit though so personally I wouldn't drink it!
Also on the side - the gym I used to go to in Japan had a 50 year old powerlifter/bodybuilder and blackbelt in judo who was the Nagasaki champion while he was in highschool. Dude was a beast. Seriously, a fucking beast! His son (who I taught) was a marathon runner, and a fucking good one at that. His youngest son (who was a fucking beast in the weight room and only 12 years old) was a sumo wrestler and ranked no. 3 in the prefecture. His oldest son is a pro baseball player in Japan. All unbelievable athletes and they ate Japanese all day - miso, tofu and edamame. None of them used any supplements either. As an anecdote - the 15 year old marathon runner weighed about 50kg soaking wet and could easily bench 75kg. For his build, age, weight and considering he could run for days, that is fucking beastly!
