There’s a wonderfully bonkers Philip José Farmer novel in which Tarzan and Doc Savage, under different names, fight through the jungle with raging hard-ons that ejaculate every time an enemy is killed. The violence is scabrous, outlandish, always penetrative. Late in the book — it’s called A Feast Unknown, from 1969 — the pulp heroes, nude, face one another on a narrow bridge, their penises swollen like a duelist’s sword. As a Star Wars parody, it beats the hell out of Spaceballs. “Beating the hell out” is the primary concern of our entertainment culture, where the Expendables, all swollen, veiny pulp heroes themselves, can slaughter dozens and still win a kid-friendly PG-13. But stick a banana in Stallone&rsq...