Theres a point in the game where your team is vastly outnumbered and outgunned by a military division. In order to gain the upper hand the player can choose to use a mortar equipped with White Phosphorus rounds. The squad itself argues if this is ethical and the conversation ends when the player character responds "No, there isn't" to the statement "theres always a choice".
If you choose not to use the white phosphorus, then you will inevitably die. The story can't proceed, even though the game keeps going, you just fight an endless amount of soldiers run out of ammo and get picked off by a sniper.
When this happens the loading screen will sometimes say "theres always a choice"
So lets say you want to keep playing and you use the mortar, after walking through the wreckage filled with fellow US soldiers writhing in agony and burning alive, you find its commander. Then he tells you "we were helping" at which point you find that they were providing relief to civilians. At which point one f your squad-mates mentions that they could have let themselves be captured or killed to avoid this.
Its not directly said "Hey stop playing" but the idea of "death' and the player to stop playing gets linked a few times in the game, so basically the NPC was saying "If you don't want to kill them, stop playing" by saying "We could let ourselves be killed"