Those situations might have been happened from the past, if you were talking about 10+ years ago, but don't think it would happens on today especially Asians/Chinese are part of Sydney's society now!!!
Yup, some Aussies discriminate Asians, i guess this happens in almost all Western countries. You should ask the guy what he doesnt let you in, absolutely can report him if he's a pure racist.
could be a gay pub/ private night club..... or the local gangs inside had conflicts with asian mobs in the past, it might be wise not to go in there, the guard just gave you a good advice.
Please reveal the name and the location of the club you're talking about.
I do find things like this likely to happen especially in a country like Australia where racism is highly prevalent, but we still need to know where did you experience this.