Hong Kong is a territory of China and they have a right to enact this law based on perceived threat to national security because this will not be the first time

Hong Kong is a territory of China and they have a right to enact this law based on perceived threat to national security because this will not be the first time USA used others shoulders to fire gun. China don’t want to make same mistake as USSR of ignoring the outside influence and USA succeeding in its mission to thwart another rising power with a different system like USS dream of Mikhail Gorbachev was broken by similar kind of violent protests. China learned from mistakes of USSR and worked to let the economic benefits trickle down to general population and their people’s life is better than before. I agree they could have treated minorities better and given more rights but looking at conditions of minority in most democratic nation its a worldwide problem. So do a better introspection and you will notice that answer for this violence and protest is very much linked to geopolitical rivalry especially with USA. There is an uncanny timings that Hong Kong protests flared up quite dramatically right before Taiwan elections, and then suddenly reduced in intensity.