I know I'm not the first on this thread to say this, but it is worth repeating: a Bastard sword is a martial weapon when used with 2 hands, and you need "martial weapon proficiency: Bastard sword" to use it 2 handed. Open and shut case.
I agree that the two swords are similar, that is why they are listed in the same group for the fighters "weapon training" ability (PF core rulebook page 56), but only a martial scholar like a fighter knows how to take advantage of the similarity.
Bastard swords are overrated anyway, it rolls 1 damage higher, on average, than a longsword. Just grab your longsword with 2 hands.