Herb Clutter had an inflexible attitude/policy toward what habit? Why?

If Herb Clutter is comparable to the hero in a Greek tragedy, then his self-righteous attitude is his hubris, the tragic flaw that results (indirectly) in his demise. He holds himself, his family, and his employees to the strictest standards: he does not tolerate alcohol, or even mild stimulants such as caffeine; he keeps his children on a short leash (Nancy is rarely allowed out of the house after ten); and he runs his ranch like clockwork.