Even saying "Australians are racist" doesn't mean you are claiming every single Australian is racist. A bit like "toxic masculinity" isn't implying that every single man is toxic

I agree with your conclusion, but don't like this analogy. The phrase "toxic masculinity" in itself identifies the fact that not all masculinity is toxic. "Toxic" identifies which strict subset of masculine behaviours are being referred to, because if all masculinity were toxic, there'd be no need to say "toxic" masculinity.

Whereas from a purely syntactical perspective, the phrase "Australians are racist" does seem to imply all Australians are racist, even if what's actually meant is that "the collective behaviour of the society made up of Australians is a racist one".

A better analogy might be ACAB, which certainly seems as though it's saying each and every individual cop is a bastard, even though that's not what it means.