Protester, demonstrator and rioter, what is the difference? These words have been thrown about in the news as if they meant the same thing; they do not. A protester is against something and wants to show the government that they are against it. The point is to show up with as many people as possible and show the government how much support your side has.
On July first 2003, about half a million people attended a peaceful protest and showed the government that they were against article 23 of the Basic Law. That article required the government to make laws on its own to prohibit any act of treason, secession, sedition or subversion. The government withdrew the new article 23 as a sensible unelected government should. A democratic government would have had the moral authority to negotiate a new article 23 with reasonable protections.
A demonstrator is someone who shows or demonstrates something. A science teacher shows their class how the world works. A political demonstrator can be for or against something. Usually they want the same thing as a protester, to show how many people agree with their stance on an issue.
In English common law a riot is a group of three or more people who disturb the peace. The wording varies from place to place, but the basic idea is the same. It is very easy to be a rioter. Anyone who is part of a group, that includes people throwing bricks, is a rioter. If you walk away, you are not a rioter. If you stop the person throwing the brick, you are not a rioter. If one finds oneself in such a situation, one must act.
As soon as violence is used by a group, it is no longer a peaceful protest. It is no longer democratic. It is a riot.
This year (2019), unlike in 2003, when there were large protests (on the 9th, of June and before) the government did not stop the amendment. Neither did the Pan-Democrats suggest reasonable changes or protections.1 On the 12th of June Legco was attacked and vandalised. It was only after that riot that the government suspended the amendment. Carrie Lam spurned peaceful demonstrations, but rewarded rioters. Violence for a political end is a dangerous path to go down. Violence may be the ultimate response, but the People's Liberation Army (PLA) holds the ultimate potential for violence.
1. While not a change or protection for the extradition amendment, Alvin Yeung and the Civic Party suggested giving Hong Kong courts universal jurisdiction to try people for murder committed anywhere. While it goes against traditional jurisprudence, at least it was a peaceful effort.