Abner Snopes is an insecure man at war with society, especially those he sees superior to him in some way. His vicious behavior suggests he lacks any self-confidence, so he rejects and brutalizes others before they can do it to him.
Abner enlisted in the Confederate Army during the Civil War, not because he empathized with the South but for his own selfish reasons. "It meant nothing and less than nothing to him if it were enemy booty or his own." His failure to choose sides in a war fought for passionate causes, leading to Americans fighting against other Americans, speaks volumes about how callous and hateful he truly is.
Abner hates anyone who has anything he doesn't, which is just about everybody because he has nothing but his wife, daughters, and son. He abuses his family, forcing them to remain loyal to him, citing the sacred ties of family bonds as the reason. He believes he's always right, and everyone else is always wrong. He creates a hell on earth for his family where they must live from job-to-job, never having a home, food, or security. The more another man has, the greater Abner's jealousy and rage.
Abner is a cold man, "harsh like tin and without heat like tin." The fires he sets are symbolic of maintaining his integrity, forcing other men to regard him with respect. The fires are emotional, representing his anger and hatred of the world. Abner has no morals and no conscience. His son finally refuses to live that way anymore.