Wait, so if the player proposes a reasonable explanation of how knocking a snake prone happens, the DM should allow it even if it makes no sense to him? Hasn't this proposition been rebutted in this thread? I thought it was you doing the rebutting, I could be wrong about that though.
Let's rephrase that, shall we:
if the player proposes a reasonable explanation of how knocking a snake prone happens, the DM should allow it even if he does not believe it is reasonable
and there you have, I think, the crux of the argument.
If the player offers a reasonable explanation, and the DM agrees that it is reasonable, he should allow it.
If the player offers an explanation that he believes is reasonable, but the DM does not, the DM should consider it carefully (or as carefully as can be without bogging the game down) and then make a ruling, one way or the other.
In either event, the player should accept the ruling, and the game should move on.....
unless the ruling is so critical as to seriously swing the game in one direction or another. In this, and only in this, case, stopping to actually hash things out is of value.
If the ruling is not so critical, after the game, it may be raised again, hashed out, and either the player(s) convince the GM or not. If not, then the GM is final arbiter within the province of any game he or she runs.
The players, obviously, are the final arbiters of what games they are willing to play in.
This is simplicity itself:
1. The players cannot force the GM to accept any rule or ruling that he or she doesn't choose to accept.
2. The GM cannot force anyone to play in his or her games, and if his or her rulings are wonky enough, the GM will soon be left in the dark, alone, wondering where everyone else went.
RC