The others let emotion cloud their judgement. They keep on trying to find "other ways" to handle the situation when they run up against the hard choices. They are conflicted and they dither while the clock ticks.
Quinn sees his duty and does it. He doesn't care what others think. With the exception of Sikes he is the only one I would want at my back for two reasons if I went down he would see the mission through and he would make sure that the other side paid.
Amazing that they try to make him the villain because of the very qualities that in real life would make him a hero.