Do you believe that the Holy Spirit is schizophrenic, telling one group of believers one interpretation and another a different interpretation? Do you believe that the Holy Spirit tells one group to baptize and another not to, one group to baptize entire families including infants and another that baptism is not necessary at all. Do you believe that the Holy Spirit tells one group to share in the Real Presence, another to have only a symbolic last supper, and yet another group to not even bother? Do you believe that the Holy Spirit tells one group that they are elect and immunized against the consequences of all future sins and calls others to repentance and contrition? Do you believe that the Holy Spirit calls all Christians to unity but promotes a recipe that has resulted in 30,000 doctrinally different churches? Do you believe that the Holy Spirit spoke a different Gospel meaning to Calvin, Luther, Wesley, Koresh, Zwingli, and King Henry VIII than He did to St. Peter, St. Paul, St. Irenaus, St. Augustine, St. Thomas Aquinas and the Blessed John Cardinal Newman? I don't. That is why Jesus left us a visible Church with a governing structure and a teaching authority to facilitate the unity we are called to.
"But they’ll latch onto anything men say in a heartbeat, no matter how absurd or improbable."
Things are only absurd and improbable in the absence of faith. When your ones personal experience, education, and reason trump ones faith the only thing that is surprising is that there aren't as many Protestant denominations as there are Protestants.
Peace be to you.
Explain the 8000+ different Catholic churches first if you want to pretend only your brand has "unity".