All that arresting peaceful protesters proves is that the government has a fear of us being united in anything. The systematic oppression of Muggleborns creates a society of Us vs. Them within the lower ranks of Wizarding UK. None of the protesters were violent. Arrests were happening before we could even be deemed as "disturbing the peace". If it was a pointless protest, why bother arresting anyone? If it didn't have power, why go through the paperwork of it all?