President Obama has recently spoken out against any "unjust" violence in Iran as a result of the election or the protests. He finally spoke out in support of the Iranian people after many had been calling on him to do so. His words alone didn't end all violence, nor did he offer Iran any consequence for it's brutality, but he did speak up. Of course, condemning the "unjust" is usually a good move for any politician.
BBC news quote Obama as saying, "The United States and the international community have been appalled and outraged by the threats, beatings, and imprisonments of the last few days... I strongly condemn these unjust actions, and I join with the American people in mourning each and every innocent life that is lost." There. Obama spoke. He still has to respect the sovereignty of Iran, he still has to lets these events play out as they will, but he has voiced his concern.
The bottom line is the only people who have the right to bring down the Iranian government over something like this is the Iranian people. If the people feel their contract with the government her been violated, they can do everything in their power to void it, as we did with the British about 250 years. Any force from outside would rightfully be seen as an act of war with Iran and would be welcomed by an opposing army. If Iran is going to change, the people need to do it. Obama has spoken, but that's all he can do.