I admire Chelsea (Bradley) Manning. She revealed many horrible things that the US was doing. Now, her opponents point out that she may have gotten some innocent people, some innocent US patriots, killed. There are two things to be said about this.
The secondary point is the one I shall mention first. There is no evidence that anyone got killed because of Manning’s leaks. None whatsoever. I challenge her opponents to bring any such evidence forward.
But the second point is this: collateral damage, or the threat thereof, is an acceptable price to pay as long as the goal is good. I have mentioned this before, when speaking about the ethics of protesting. At that time, I said that I could not support a protest which targeted the innocent, no matter how good the goal of that protest might be. However, I would support a protest that targeted the guilty, even if it ran the risk of also harming the innocent.
Manning’s revelations (and also Snowden’s and Assange’s) fall under the same sort of reasoning. I support them because the goal was good: to reveal great injustices and wrongs, which the world has a right to know about. Even if people were harmed in the process, even if innocent people were harmed in the process, that is collateral damage that is fully justifiable for the goal.
I support Manning for the same reason that I support dropping the atomic bombs on Japan during WWII: yes, both may have run the risk of hurting innocents, but both had an excellent goal (the difference being that Manning stood much less chance of harming innocents than the atomic bombs, of course).