Also, in the 1980s, nobody knew exactally how AIDS was transfered or what caused it. At first, it was just the "gay plauge" since most cases were amoung gay men. At that point, they could not have prevented it either, since they didn't know how to.
Also, condoms aren't foolproof. They don't always work. You can have all the safe sex ya want, but you're still at risk for AIDS.