DMZ2112
Chaotic Looseleaf
When a fighter pushes an elephant, he startles it and threatens it so it takes a few steps back. When he slides an iron golem, he figures out its attack pattern and steps in a way to prompt it to lunge where he wants it to end up. When he trips an ooze, . . . well okay, that doesn't make any sense. But 'viscous fluid' as an enemy doesn't make much sense in the first place.
It's not a matter of explanations. A sufficiently creative mind can explain anything; I know that. And if that's how you want to run your game you should feel free, but those of us who /want/ to limit player control of the battlefield ought to have the tools to do so without being reduced to "because I said so."
I /understand/ the playstyle that believes that the fighter should have the ability to narrate the effects of startling an elephant, or sidestepping an iron golem. I do. But when that playstyle is the only one supported by the ruleset, it makes it very difficult for the DM to justify saying "that doesn't work because {perfectly logical reason}," which is important.
I'll be perfectly honest -- I don't personally believe in compromise between the DM and the players. I'm an advocate of absolute DM authority. I think that's his role and I think it makes the game more fun (when it's done well). But at the very least, the rules have to permit narrative compromise, and dictating that a tactical "power" has a specific, non-negotiable effect on the battlefield interferes with narrative compromise just as much as leaving the effect of the "power" entirely up to DM fiat.