Well, I would suggest that the options are there (for the "Lawful Good" character to axe-murder all the liitle children in the route to the dragon he must deal with): certainly this would have a dramatic effect on the PC's alignment ... :D
I don't think the game's engine is there to nanny the gamer, merely to provide the framework for people to do anything. Reputation, I feel, helps balance the alignment choices made by the character; this can be augmented by some sort of historical "background" quality as well, for in-game NPC biases (oh, you're a dwarf: we elves hate your kind).