So basically the research is all over the place. In fact, one study put the testosterone and DHT levels of rats fed a high phytoestrogen diet at higher than a non-phytoestrogen diet.
(PubMed) How that makes sense, I'm not sure.
Your best bet is to consume a decent amount of soy. Moderation in all things as usual. Soy as a protein is not the only protein enemy. Meat contains steroids, has been proven to aggravate estrogen levels and can further gynocomastia. Casien can cause gastrointestinal distress. You could have an allergic reaction to whey.
In all reality, whey protein is vastly superior. But it is not the only suggested option. Soy can be great for you, for every negative study, a positive one negates it, as is the case with many medical studies. In time, further studies and hopefully human studies will show us just how soy protein works, its short and long term effects, and how to properly use it.
So just figure out what works for your body. Probolic-SR and Up Your Mass from MHP are soy based proteins and I have found them to be superior to many of the protein drinks I have tried. I also am a vegetarian and consume soy based products. Everybody's body is different which is why no one supplement will work exactly the same for everybody. Keep doing research, keep an open mind, and never settle for any one product, researcher, or study.