Many times vegans actually raise the point that all the water we use to grow the soy

the vast majority of the global soy crop (about 85%) is pressed for soybean oil for human use. the waste product from that process is called soy cake, and if it were not fed to livestock, it would simply be industrial waste. feeding soy to livestock is a conservation of resources.

https://ourworldindata.org/images/published/Global-soy-production-to-end-use.png