Sinn Fein are the enemy. All very well and understandable, you may say. It's just language. It has been pointed out that the notion of enemy always connotes at least the potential for killing him as a viable and legitimate way of resolving disputes. Even if we don't follow this analysis all the way, it should give us occasion for some serious thinking.
Enemies are expendable.
Enemies have no personhood. Enemies can die. When we see someone, or some group, as the enemy, war is the only appropriate means of confronting them. Of course from the Christian perspective, there is the injunction to love our enemies. We have to find ways to overcome the enmity.