That's where I lost all respect for the Gibson character in Signs. What self-respecting farmer doesn't have a shot gun? If he cares that little for the safety and protection of his land and children, why should we care? He's got something messing up his crops, so he cowers in the basement!
It was insane. I understand he was a priest. But a shotgun on a farm is a tool. Rabid animals,pests all need to be taken care of. We know from the film the aliens could be harmed. (chopped off fingers)
And I understand barricading in the basement. But come on.
Plus the brother acted either doped up or retarded. ;o)