Self-taught artist Elmer Wayne Henley claims that the act of appreciating nature “calms the soul” — “it proves to me that there’s a God,” he says, and so his rather naive paintings depict flowers and landscapes. Henley is serving six life sentences for the sexual torture and murder of dozens of young men, and whether he deserves a calm soul is a question wisely left unexplored in this chilling documentary. Instead, director Julian P. Hobbs focuses on the hobbyists who create the market for the artistic works of serial killers, people like Baton Rouge mortician Rick Staton, who enjoys the “brush with deviant celebrity” and shares his snapshots of chummy prison visits with such notorious murderer/artists as John Wayne Gacy; Joe Coleman, an artist in his own right and collector of death memorabilia, who likens the crimes of serial killers to “pagan rituals”; and Tobias Allen, creator of an infamous serial-killer board game, who says his “obsessive” pastime is an attempt to figure out “what kind of person” commits heinous murder. That’s the question that underlies Collectors, though Hobbs approaches it indirectly and from the opposite side: Is there only a degree of difference between the likes of Staton and Allen and the likes of Henley and Gacy, and is an interest in abnormal human behavior abnormal in itself? It’s impossible not to sympathize with the angry families of murder victims who wonder here how anyone can glorify killers and lend to their notoriety, or with the victims’ right advocates who, incredulous, sputter that these collectors are “pathetic.” And it’s also impossible to fathom that Staton isn’t the least bit creeped out by a portrait of his own very young son by Gacy, who killed little boys like him, and that Allen honestly sees his game as “a spoof on war games.” How far can black humor go before it crosses the line into from mere tastelessness into abject inhumanity? And does the fact that I enjoyed immensely this gruesomely mesmerizing film mean I’ve crossed that line?