You have to look at this issue from a Hong Kong resident point of view (I am not a Hong Kong resident). Since the handover to the China government, the average living cost is higher than ever before [1], real estate price skyrocket due to huge amount of investment from China[2]. Some Hong Kongers may blame these issues to "mainlanders" for "disrupting" their live.

Also in 2013 "mainlanders" rush to Hong Kong to buy milk powder due to the poisonous milk power scandal in China, causing a shortage of milk power in Hong Kong [3]. I certainly wouldn't be happy if suddenly I can't buy milk power for my child because my neighbour had bought all of them.

[1] https://www.scmp.com/news/hong-kong/article/1143157/hong-kon...

[2] https://www.scmp.com/business/article/3002396/hong-kong-home...

[3] https://www.worldjournal.com/6148953/article-%E9%A6%99%E6%B8...

Interestingly a lot of HK people here feel the rest of China is looking down on / showing no respect to us and everything that makes HK different from the mainland.

Mainlanders don't share etiquette & hygiene standards that HK has from the west. If China would import anything besides human rights...

This relationship between Hong Kong people and mainland people is quite similar to immigrant issues in the West. Mainland immigrants are perceived to not work, receive free apartments in the world's most expensive city, and have poor judgment in things ranging from politics to obeying the call of nature.

Well, at least they are interested. Today evening on a metro, I think quite a few people were watching videos on HK events