It is important to use precise language. “Australians are racist.” is simply false if even one Australian is not…. So you should instead say, “Many Australians are racist.” or “Most Australians are racist.” or “On average, Australians are racist.” Those claims may or may not be true.
Also, if you make a claim like that with no source except your own experience, it’s safe to assume you’re wrong, that you are extrapolating when you should be doing research instead. Australia is a big country and you have met a small fraction of the people in it.