I uninstalled both Civilization V and Steam, reinstalled while keeping the automatic update features off. Steam forced the update anyway. There is no way to avoid it, and once you have the latest update to Civilization, Thal's balance mod will not function.
Currently there is no solution until Thal fixes the mod. The Diplomacy mod works, however.
My advice is to go into steam and change Civilization V game properties to "Do not automatically update", play in Steam offline mode, and when Civ V is updated wait until people in the forum confirm that the balance mod still works. Then update Civ V manually through steam, and make sure the "Do not automatically update" setting stays put (Steam loves to switch it back in a sneaky fashion). Check this setting every time Steam launches your or you run Civ V.
Note that any saved games using Thal's balance mod, will crash the latest update of Civ V. So they are basically wiped out.