My diet includes a lot of soy products: soy milk, tofu, and tempeh mostly. But soy is used in so many vegan products as a source of protein. Many people believe too much soy is harmful, and can even add to the higher risk of cancer. Before we throw the soybean under the bus, there is a lot of misinformation circulated.
Moderation is key in everything, so eating a diet that is mostly soy is surely not recommended. However, soy has been unfairly accused of being overly harmful. That last link was from an admittedly pro-vegan doctor. Trying to find a neutral party, this Harvard School of Medicine article on soy seems to say that soy is both not harmful, and may be harmful.
I’m going to stick to moderation as key while scientists continue to research this topic. As a personal experience, I am going to avoid soy for one month and report back with my results.