I start by stating that I recognise this is another nail in the coffin for the freedoms of HK and the penalties are draconian and unwarranted.
However if we take the Anthem in isolation and compare usage of Star Spangled Banner in US there is a bit of double standards going on.
I’d like to see someone attempting to abuse the US Anthem in a US sports stadium. There’s no laws against it that I’m aware of but I’m pretty sure some ‘justice’ would be forthcoming.