Might be useful to look at the context of this "rude behavior" by the cops.
About 200 people, who had participated a little earlier in the demonstrations against the health pass and compulsory vaccination for certain professions, left the authorized processions to head for the Champs-Élysées around 5 p.m.
The police, CRS and police quickly intervened to try to block access to the avenue des Champs-Élysées, visibly taken over. Dozens of demonstrators began to descend the avenue des Champs-Élysées towards the Place de la Concorde, shouting for “liberty, liberty!”, Before singing a Marseillaise, while lines of CRS were deployed without however cutting off traffic on sidewalks. Visibly overwhelmed motorcycle brigades and mobile units of CRS came and went to try to block the eastern and western accesses of the avenue to the demonstrators who then deployed in scattered groups.
At around 6 p.m., the situation became more tense when demonstrators erected barricades and threw projectiles at the police, who retaliated with tear gas canisters and water cannons, as tourists walked along the avenue. .
Does that answer your question? The protests were authorized and were expected to follow a certain route which a small minority (200 out of 11000) was not happy with, just as they were not happy being peaceful. So what's missing, dialog-wise? Note that protests in France have an occasional tendency to become violent and trigger property damages, especially to cars. Expectation of property damage, which is mentioned later in the article:
Storekeepers then hastily tidied up their terraces, lowered their curtains and closed shop.