Someone beat me to the punch on Romans 13 dealing with the fact that the God has given a "sword" to the earthly government and when they use it they are doing his will.
In addition, when Exodus 20:13 is PROPERLY translated it reads: "“You shall not murder," which is very different from "You shall not kill". Murder is the unlawful killing of one human by another.
Also, Isaiah 2:4 " They will beat their swords into plowshares and their spears into pruning hooks. Nation will not take up sword against nation, nor will they train for war anymore," refers to a future time. Not the present.
The preaching work is an epic fail argument. There is a list of religions that carry on in a public preaching work.