I can't say the police did the right thing. Protection would have been far better, even though the protestors were a riot waiting to happen. They should have been prepared for that eventuality, too.
I wonder what LE would have done had the roles been reversed. Let's say you or I called to say that we saw someone from that El Salvadorian gang with a gun. HA! Highly unlikely that LE would have gone busting into a crowd like that to find out who is and isn't carrying a weapon and arrest them. Fat chance. Which is why the illegals and their supports should never have been allowed to assemble is such large masses, beyond the control of local LE