Since there was really no way to determine anyone's prior intent, who they were and who the pair might have represented was largely irrelevant. They could all have been arrested for a number of misdemeanor offenses. In fact, there should have been mass arrests. This was not a protest, it was a brawl. Elements of both sides arrived determined to engage in violence. While some involved may have truly sought to engage in peaceful protest, too many were itching for a fight, and in spite of a lot of advanced notice, the police chose not to beef up for this event.
The police in Berkeley effectively stood down for a number of reasons, not the least of which was a lack of manpower to effectively intervene. And, quite frankly, from the police perspective these days, there is less liability to do nothing at all than to act and engage in physical confrontation. In the end, by the time Oakland PD arrived with effective numbers, much of the violence had already dissipated.

