Whether the police or the protesters in Genoa used force first doesn't matter. The elites which the cops are defending have done a hell of a lot more violence to ordinary people then protesters would dream of doing even to the elites. In that context, any violence used at this protest is basically self-defense by the working class against the exploiting class.
Joe R. Golowka
"It is not enough for a handful of experts to attempt the solution of a problem, to solve it and then to apply it. The restriction of knowledge to an elite group destroys the spirit of society and leads to its intellectual impoverishment." - Albert Einstein