Democrat Alexandria Ocasio-Cortez compares the number of police in riot gear to the Freddie Gray (Baltimore) and Eric Garner (New York) protests and the gun-rights protest that happened in Virginia. She says there's almost no police officers at that protest and suggests that the institutions are racist, without specifically saying that.
However, one should point out that when Freddie Gray protests happened, that turned into an actual riot and there were 486 arrests. During the Eric Garner protests, the same thing happened - lots of arrests. During both the Freddie Gray and Eric Garner events, there was a lot of things being damaged.
During the gun rights protest in Virginia, there was one reported arrest and no damaged buildings or looting.
So basically, when a protest turns into a violent riot, that's when the cops in riot gear show up.
It's really that simple.