Another element often found in zombie films is the freakiness of familiarity the victims seem to have with the creatures attacking them.
When the main character is attacked by a zombie who was originally a friend or a loved one and want to turn it into his next meal, there are no limits to sheer horror.
No matter how well you used to know a person, as soon as he or she dies and comes back to life, all bonds are broken and you are now no more to him than the next meal. Brother devouring sister or daughter devouring mother and father are commonplace in the modern zombie films.
The unity of the family is then broken by the zombie plague. Night of the Living Dead also succeeded in shattering taboos of family and personal relations that had, until that time, been left untouched by American culture. Upon transformation into zombies, the characters in the film lost all moral responsibility, allowing them to indulge in such monstrous activity as incest, cannibalism and paricide.
In the late 1960s, America was brutally confronted to the horror of the Vietnam War. With the brutal onslaught of gruesome imagery generated by the media buzz surrounding the war, America no longer needed "monsters" to scare them. The horror generated by mankind was scary enough. Night of the Living Dead capitalized on this by resorting to the same nihilistic attitude toward death and destruction that was generated by the war.
The zombies appear as the archetypal monster of the modern times, combining various elements from the other myths : they devour like werewolves and infect by biting like vampires. But their power is limited, they are slow and weak and possess no supernatural abilities. Their only strength is their number.
The second difference with the previous monster archetype is that this monster is “empty”, he acts much as the Golem, a death puppet. His absence of motives echoes the absurdity of the Vietman war, and the deep scars it left to America.