This sounds like a claim that wars happen because of weapons. Protesters, and police sometimes have incompatible goals (say crowd wants to block traffic somewh

This sounds like a claim that wars happen because of weapons. Protesters, and police sometimes have incompatible goals (say crowd wants to block traffic somewhere, and police ordered to prevent it), and the conflict is inevitable in such circumstances. It's a little naïve to claim that it would not happen if one, or even both sides would come unprepared for violence. Deescalation is preferred way, but it works as much as either protesters would be ready to back off (and some protesters may see it as a surrender), or political power giving orders to police is ready to let protesters get what they want (and it's not always possible for them for variety of reasons). Also, ability to show force often plays a role in deescalation strategies.