Here’s my (fallible) understanding of the nugget of truth behind the soy nonsense.
Plants contain something called phytoestrogen. It has a similar shape and function in plants to estrogen in humans. Soy contains a lot of it.
However, since it is made of different chemicals to estrogen it does not act like estrogen in humans.
Still, because it has the word “estrogen” in it, a lot of idiots think it will cause you to become weak and grow tits if you eat soy. You know, like a woman. Hence the “soyboy” memes and the use of the term as an insult, mostly by woman-hating alt-right goons.
It’s possible your friend is covertly falling for the fallacy, or perhaps their concern is several times removed; i.e. they fell for someone’s lie based on a lie based on a lie based on bigotry.