Not relevant at all. The government cannot be trusted to gather lists of protest attendees since they would be immediately used for retaliation.
Statistics can be looked at in aggregate. Infections did not go up in areas with large protests.
The BLM tribe has safer Covid behaviour in general than the other side, though, outside their protest attendance. That's a pretty big confounding variable.
that's why the authors of these studies have been using anonymized cellphone data to study concentrations of people and subsequent changes (if any) in case loads.