I don't see how "there are monarchists in Parliament" is a refutation of "this treatment of people protesting the monarchy is a strong argument in favor of abolishing the monarchy"...?

Those Monarchists were elected. I'm sorry that sometimes people you disagree with get elected. Regardless, it's the police who are enforcing this law passed by Parliament... I don't believe the law even mentions republican protests. You are blaming the Monarchy for the acts of the Government and Parliament.