If you screen HIV from the blood supply, no one gets AIDS from a blood transfusion.
While it is a fact that the connection between HIV and AIDS wasn’t found through traditional methods, you can’t argue away the connection between them.
And before we knew to look for HIV in blood donations, a number of people got AIDS from transfusions.
So what NEW virus may be rapidly spreading through the homosexual community via promiscuous anal sex, which we don't know about? It's a GOOD idea to exclude blood from members of a community which is a known disease vector.