If San Fran’s Board of Supervisors gets its way, ’80s-era warnings about the dangers of amyl nitrate -- a.k.a. poppers -- will be back. Because the scratch-and-sniff treats increase rates of HIV infection -- the chemical “lowers your defenses” majorly and brings blood vessels to the surface of skin during sex -- pols are calling for point-of-sale red lights. Activists are split, with Survive AIDS making approving noises, while others mock the measure as authoritarian.