The reason why this is a peaceful demonstration, because it is in Hong Kong and police force show very good professionalism. If a police officer gets a complaint, he is in deep shit. There is a committee that oversee complaints and also there is ICAC that overlooks for any corruption among the population including the police and the ICAC itself. If it was in any other city, any physical provocation by the protester could initiate baton beating and macing from the Police force, and would be noted as "justified".
In my opinion, some people had higher expectation when government change to CY. I had some high expectation and I was disappointed when some did not go through, but he still manage to balance it out and I was happy with that. The opposition kept targeting his credibility and kept CY from successfully enact some of the policy that he promised. This also caused unhappiness with the government by the populace.
The opposition kept targeting CY for the illegal addition to the house, which a lot of rich people and opposition members probably did the same thing to their house (Very common in HK). The Chinese pregnant women coming to HK "overcrowding" hospitals, CY put a full stop to that, and caused panic in private hospital. (I think somewhere they mentioned that hospitals back in the 80s could probably handle the amount of pregnant women, but bed slowly decline due to birth decline). The main problem about social housing, where he tried to get land from regions, he faced with opposition from the locals (social housing degrade the price of the neighboring buildings). The bridge that would connect Macau, HK and China was temporarily halted on the HK side.(This was caused by an old lady stating that the bridge had environment impact and went to court. The old lady was later found to have no knowledge on how to do this, but it was the opposition that used her as a figure head and pulling string from behind. This has caused the gov't to overspend on the bridge due to delays and material cost increase.) The most retarded case in my opinion was the milk powder shortage. People kept blaming the Chinese and did not blame the businessmen for not increasing supplies. Chinese did not suddenly overnight came to HK and buy out all the milk, it happened over a period of time, and it was hastened due to the poisonous milk incidence. CY again enacted limits on how many people can bring back to China. In the end, when all these add up, along with those that I didn't mentioned, these have negative effect on the government, but if people actually look at the details, they would definitely see what caused the current government not able to do many things. If it was the British government, things just get enacted and opposition could be crushed
