parasite is a some what loosely defined term. From Wikipedia: "In medicine, only eukaryotic organisms are considered parasites, with the exclusion of bacteria and viruses. Some branches of biology, however, regard members of these groups as parasitic."
The cause of "HIV" has never been established with absolute certainty. One theory comes into focus, someone claims they have discovered the cause and cure and then over time that supposed fact fades away and another cause / cure is touted.
Just because the AMA touts something does not make it fact. Historically many known "facts" are ultimately proven false. The earth was flat--until it was round. Doctors ridiculed and drove out of their profession the original physicians who advocated washing hands to reduce cross contaminations between patients.
At this point the question of the core cause of AIDS is open--anyone saying otherwise is spouting a theory as fact.