Definition
(adjective) [1] Pertaining to atavists. [2] Relating to old or established pattern; habitual, ingrained [3] (as a noun) an atavist is a genetic characteristic emerging after absence from several generations (see Wikipedia entry for a more detailed explanation).
DFW's Sentence Or you could call it atavistic, a throwback. The truth is that what we think of as objectivity in journalism has been a standard since only the 1900s, and mainly in the United States. Have a look at some European dailies sometime.
My Sentence I apologize Sir, but what you are observing is not an alarming atavistic regression, as you call it, into tribes of selfish brutes, but quite simply humanity's continued inability to spiritually evolve and I'd suggest you not let technology obscure your vertical view of human history for if you take away the gadgets we're still stuck with the central question which is, plainly, how can we live with one another?
01: DFW Source: The Host
02: Definition Source: Wiktionary and Wkipedia