It makes me wonder if they actually watched the same scene I did, when I played the game.
I watched a soldier get caught in an earthquake, which knocked him out. When he woke up, it was dark, he was separated from his squad, and surrounded by enemies who'd kill him on site. He went crawling through the area which had the rat, in his effort to sneak to safety. When he ran into the rat, the soldier tried to shoo it away, before it squeeked at him, and attacked his hand. Taking reasonable measures for his own safety (not wanting to be bitten by a potentially diseased animal, and not able to put up with ANY noise in his current situation), he kills the rat, and then places it out of the path in front of him.
In the scene, I actually had a feeling that the soldier didn't want to kill the rat, since he initially tried to shoo it, even when the rat was trying to bite him. It felt like he was forced to by his circumstances.
How this scene would offend an animal activist, is beyond me.... and I'm actually a little offended by the people who are offended. Surely, the soldier's life should be viewed as worth enough, to not be compromised by a rat... but, are we absurdly trying to suggest that the soldier should have put his life at risk by allowing the rat to continue to bite him, and make noise?