Is it true that soy beans are bad for men sperms fertility?

Unlikely. : You are correct in that soybean contain phytoestrogens, which have weak hormonal activity and theoretically can reduce fertillity. There is, however, no conclusive evidence that it does, and many cultures which consume large amounts of soy do not have appreciably different rates of paternity and infertillity. No randomized trials exist, however, and this is an area of intense study.