Boromir 'assuming that the Company will go through Minas Tirith'?

[Flammifer]

This has been stated in the class as though the route through Moria would not necessarily go through Minas Tirith. Boromir has no reason to assume that a route through Moria would not go through Minas Tirith. The only way to get to Mordor is to cross the Anduin. Boromir knows of no way to cross the Anduin short of Minas Tirith. He does not know that the Company can stop in Lothlorien and get supplied with boats, allowing them to cross the Anduin before reaching Minas Tirith.

So, I think that Boromir thinks that all possible roads for the Company go through Minas Tirith, and aversion to the route through Moria is not due to any inkling that that route might avoid Minas Tirith.