So are you saying that historical fiction should not try to capture in as vivid a manner possible the realities of time and place? Webb would be doing a DISSERVICE to the genre by watering down/censoring the atrocious behavior that did occur in real life within this temporal framework. Just because it's fiction doesn't mean it has to be unrealistically rosy.
Webb's inclusion of these explicit scenes could just as well be taken as a profoundly negative commentary on them.
Maybe all new fictional works based on 9/11 should not include the Towers being hit and falling down, or the planes being hijacked. Because, you know, that's murder and heartbreak, awful things really.
That's a beauty of a strawman, but I fail to see how the man-on-boy fellatio or the banana slicing are critical to establishing the realities of time and place. It seems more like gratuitous "spicing up" of the prose to keep the reader's attention. At that level, the kinds of "spicing up" selected by the author are highly relevant in judging his character and what's going on in his (sick) mind.