Before rushing to judgement about the incident of the old man being sprayed, consider these points:
1. The officers who actually sprayed him and the other protesters are behind two lines of other officers directly facing the protesters. That means it's unlikely they saw them clearly or evaluated their age. They would only have seen a group not moving and therefore initiate spraying to move the group along.
2. The officers were obviously ordered to clear the area, and moving in formation. Do you expect the officers to walk around them and let them stay there? Of course not. So they can either arrest them, push them back, or spray them. I would think spraying would be the first option, and if they still don't move, then physically push them back with their shields, and if that doesn't work, start arresting some of them.
3. Were the protesters in a space where they were legally allowed to protest? Remember there are protesters and there are citizens who are against the protesters. The police are supposed to enforce the law and protect the rights of all citizens according to the law. I am one of those who believe that if you initiate a confrontation, you bear at least some responsibility.
4. If you disagree with point #2, then tell us what do you think the officers should have done in that situation. If the officers followed your suggestion instead, how would the officers be judged or evaluated by those giving the orders to clear the area, and by the general public who believe the area should be cleared as ordered.