When clashes are protests and when protests are clashes

It is easy. When the government is a client of the US, the protests are described as "clashes" to justify the murder of civilians by government. But when armed protesters attack a government that is a foe of the US government, the armed protests are described as "peaceful protests".  The Yemeni case is quite illustrative. No one doubted that the protests in San`a were peaceful but they are "protests" in the Times.