There often isn't much difference between the ethics of a 'legitimate' ruler and the ethics of a mob boss. Obama has happily signed away some very important, very basic rights of his citizens in order to further a completely unnecessary war as well as been responsible for plenty of assassinations and combat deaths. (Note that the Republicans would probably have done the same but worse, this isn't about partisan politics.) However, when he does things they have the stamp of legitimacy. He sends in official type people on missions that are public because no one can do anything about it; Osama Bin Laden simply wasn't able to prevent himself from being killed regardless of the fact that he knew it was coming.
On the other hand you have the Pakistani railways minister who was extremely angry that a random person in another country made a film that offended his religious sensibilities so he put out a $100,000 contract on the life of the filmmaker in question. He would have happily started a war or sent a strike team to destroy the filmmaker instead but of course he lacked the direct power to do so, much like a criminal does. Drug dealers may beat people up but they don't do it publicly and acknowledge it when asked; contracts are the weapon of the underdog.
That stamp of legitimacy is simply power though and has nothing to do with moral authority. I think both the press and regular people often confuse the two and talk as if someone in a suit giving an executive order is somehow better than a machine gun wielding militant hiding in a cave when their aims and results are the same. Dropping bombs from high tech planes on civilians isn't better or more justified than shooting those civilians at close range because the only difference is how powerful the aggressor is. Power should not imply moral behaviour or appropriate goals though unfortunately people often see it that way.
I find it hilarious that Obama went before the UN to condemn extremism and violence after his nation invaded another nation and caused more than 100,000 civilian deaths. Certainly the violence of the protests in recent days is deplorable but it is a pittance compared to the violence of the Iraq war. It must also be noted that the US is happy to imprison and kill people without due process, just like any terrorist organization, when it suits their needs. The difference, again, is simply that they are powerful enough to do it publicly and nobody can stop them.
Stopping violence is a good thing. Spreading democracy and basic human rights around the world is a wonderful goal. The first thing you would want to do to make that happen though is to set a good example. You will win nothing but enemies and accusations of hypocrisy when you cloak violence against the weak under the guise of self-defence and then condemn others who do the same thing without as many guns to back it up.