Here's what the police should be doing to break up these mobs equip some undercover officers with some myotron pulse wave devices . ( these are not stun weapons )
These groups are prepared for water cannons and pepper sprays attacks.
The myotron is small enough to be held within one's palm. All it takes is a second for the person touched to lose all voluntary muscle control ( including bladder control ) and be completely immobilized for up to 30 minutes.
Just have the officers start in the middle of the group , moving around from target to target , the larger the target the more will be needed to help carry the target away.
As more and more go down , the remaining mob will panic , not known what is happening. Leaving the leaders at the front alone and easily controllable.