Reason the government and general Australian public "scream about boat people" is because every terrorist attack in Australian history has been committed by as you quoted, "undesirables" and Australia as a nation is trying to avoid a similar situation to many European countries where terrorism is an genuine concern for the everyday citizen. Personally, as an immigrant to Australia (the most beautiful country in the world), moving here from New Zealand at three years old, I have never had a problem with the Australian government and have received my citizenship, but thats because you dont see Caucasian, Asian, Indian etc migrants running through Melbourne stabbing people in the neck, you dont see them taking 18 hostages in cafes in Sydney, you dont see them shooting accountants in Parramatta, I could go on with hundreds of examples, here is a wiki page of Aussie terror attacks and the problem is so blatantly clear, middle eastern refugees and migrants. Before you respond with the default script of "you're a racist not all of them are terrorists" of course not. There is always bad eggs, I know this, and even in a country with no immigration there would still be crime but they have a stigma around them because it is justified, they without a doubt commit drastically more terrorism than any other group of people and whether it be their religion or mindset, thats not my problem. Being worried about being the victim of a terror attack should also not be my problem, but it is, and the only way for Australians to feel safe is to stop middle eastern migrants and asylum seekers from entering into our country. I have made many middle eastern friends at university and have met many lovely people throughout life, but unfortunately, if the chicken is laying too many bad eggs and making the farmer sick, you've got to change something.