Any action by Israel in defense of its national interests is always condemned by the "international community." But the IDF video below is pretty conclusive. See, "Video Update: Demonstrators Use Violence Against Navy Soldiers Boarding Ship." (Via Memeorandum.) And at Haaretz, "Israeli commandos: Gaza flotilla crew tried to lynch us."
A second IDF video shows Israeli forces communicating with the flotilla:
Further, the "peace activists" invoked the killing of Jews:
And breaking at Jerusalum Post, "Netanyahu cancels upcoming Obama meeting, returns to Israel."
Background reporting is at Wall Street Journal, "Israeli Clash at Sea Inflames Tension."