The foreign ISM activists try to penetrate the line of soldiers and even use a bike to ram a soldier. Later they refuse to disperse when told to move back. If doing this isn't provocation, what is? If I live in a city and come across a policeman who tells me to stop moving and not to cross a line, and then I do the opposite of what he tells me, I'm going to expect him to use force to stop me since his instructions didn't.
Report: Iran's Culture Ministry refuses to allow Barenboim to perform in Tehran (DPA)