Killing in God's Name

Lately there has been a lot of talk about killing in God's name (usually by someone claiming to be a member of "the religion of peace"). Are there Biblical precedents for such an attitude or belief? Let's consider:

God gives us early encouragement not to kill, in the case of Cain VS. Abel...

Moses killed a man, but then God chose to use him to lead the Children of Israel out of Egypt anyway...

God gives Moses the commandment, Thou Shalt Not Kill...

But, then, God becomes angry at King Saul for not killing...

But King David got in trouble for killing...

In addition, under Old Testament Law, there were allowances made for killing for revenge. If someone killed a relative of yours, you had a right to hunt them down, unless it was an accident, and they were able to get to a city of refuge before you got to them...

It gets complicated. But, realistically, under the new covenant, we don't have to worry about such things any more. Jesus made it real simple: Turn the other cheek. Interestingly enough, Jesus made that comment very shortly after referencing the Old Testament eye for an eye... Something that has been attributed to both Ghandi and Dr. Martin Luther King Jr., is that "an eye for an eye just leaves everyone blind." Certainly that's true. As I have posted before, we are imperfect people, seeking to do the perfect will of God, and sometimes we get it right. But we make a lot of mistakes along the way. I would hope that no one dies because of my mistakes, but I can't guarantee that. If someone dies, who then has the right to kill me? God didn't grant anyone the right to kill Cain... It is important that we forgive each other, because there is not a one among us that will never need forgiveness.

The bottom line is, in the modern day, killing in the name of God is wrong. period. I don't care if you are talking about killing people who refuse to accept your religion, or your way of thinking, or whether you are talking about killing abortionists. Thou shalt not kill. God likes mercy, and we need God's mercy.