Soy is bad? Not really... it definitely has it's uses.
The 3 isoflavones in question have weak estrogenic properties but have a high affinity for the estrogen receptor.
So, there action can mean a few things. If you have high endogenous estrogen levels, the soy isoflavones can compete for the receptor, blocking some estrogen, lowering the estrogenic affect on your body.
If you have low endogenous estrogen (a healthy male), the isoflavones will bond to the receptor and cause a slight increase in estrogenic activity.
As you see in the first instance, soy can actually be used in the same sense as clomiphene citrate (but it has properties closer to that of nolvadex).
Basically, IMHO, soy is just not an optimum source of protein (and overall nutrition). It's not bad persay, but it's not the best choice you could be making. Who wants increased estrogenic effects (retain water, E fat etc)?
Brain shrinkage? Thyroid issues? I haven't heard of those ones...