Plenty of straights get HIV - through tainted blood and whatnot. One reason the mere thought of blood banks allowing queers to donate is outrageous...
Some, not plenty. I recall hearing an interview on a radio program many years ago- back in the late 70s, I think, in which a militant homosexual said that they planned to donate blood as often and widely as possible to infect straights. That, he said, was the only way AIDS research would be adequately funded.
Also remember that before AIDS it was called GRID- Gay Related Immuno Deficiency.