You gets AIDS one way, you give it to yourself by stupid, careless or reckless behavior. There might be a tiny number of people who got the disease in other ways, but 99.9% of the cases are transmitted by irresponsible behavior.
AIDS is not spread by coughing on a bus, sitting on toilet seats, or drinking contaminated water. It is spread by exchanging bodily fluids, mostly through sex or needles. After 30+ years of publicity, only the most retarded of people do not know this.
So if a person is stupid, careless or reckless enough to infect himself with AIDS why should anyone assume he will change his behavior and not spread the disease to others? Answer: There is no reason to think their behavior will change. Keep them out of the country and quarantined from others.
AIDS is a stigma. It is a stigma of stupidity. If you dumb enough to give yourself AIDS, it is in the best interests of humanity to remove you from the gene pool.