I don't think trying to put the blame on a single person is reasonable.

In this situation, the GM "set up the trap" by crafting a situation that can easily degenerate and ruin the game, and the Player "pulls the lever" by choosing character consistency over preserving the game (or what's remaining of it).

[Then, depending on how the GM and the Player continue to react, they might be either sending some rope to the poor game at the bottom the pit, or pouring some oil in the pit and starting a big fire]