Is it ever okay to lie? For most, the quick, gut-level response to that question is "no."
But let me ask you this: if a burglar broke into your house carrying a weapon and asked you if there was anybody else in the home, would you say, "Yeah, actually, my kids are hiding in the closet." Of course not. In extreme circumstances, sometimes we are forced to choose the lesser of two evils. Lying is wrong. But, when faced with the safety of your family, it can be the best option.
With that said, how should Christians react to the death of Usama bin Laden? Extending the "lesser of two evils" analogy, I think there are a couple of things to remember:
1. Not choosing the lesser of two evils is, essentially, choosing the greater of two evils.
2. The lesser of two evils is still evil.
Number one should dictate our actions. Number two should dictate our emotions regarding those actions.
When given the choice between two evils, we must chose the lesser. That might mean voting for a candidate who doesn't completely line up with your beliefs. That might mean speeding to get to the hospital with an incredibly sick child. That might mean using a baseball bat to get an intruder out of your home. That might mean taking the life of the mastermind behind the world's largest terrorist organization. None of these is ideal but, given the circumstances, they are better than the alternatives.
Are there biblical examples of this? Yes, plenty. David killed Goliath (1 Samuel 17). Joshua toppled Jericho (Joshua 6). Gideon fought the Midianites (Judges 6). Each event came at God's specific direction and involved the loss of life in exchange for the protection of others.
When choosing the lesser of two evils, we must not delight in the deed but rejoice in the result. Bending our beliefs, breaking the law, and being physically aggressive are actions that, in a world as God intended, would never have to occur. Rejoicing in anything evil - even if it is the best alternative - is dangerous. It desensitizes us from the gravity of the decision, and makes such choices easier in the future (with or without justification).
1 Corinthians 13 says, "Love does not delight in evil, but rejoices with the truth." On Sunday it seems as if the lesser of two evils was done. But, as Christians, we should not delight in that. Evil is evil. Rather, we should rejoice in knowing that the alternative would have been much, much worse.