Joe Keller has more than one excuse for his crime. He rationalized sending the faulty parts to the army, even knowing that they would cause death for young pilots, because he feared what would happen to the business he worked so hard to build if he didn't fulfill his order.
His fears come to the forefront in what he considers a dog-eat-dog, every-man-for-himself world. He states that nobody would care that he worked forty years to build a successful business, but would pull his contracts and shut him down in a minute if word got out that he had made a mistake and produced shoddy parts. He argues that the risk to his business and the financial well-being of his family was too great to pull the parts. In a final burst of rationalization that allows him to live with himself, he states that he assumed someone down the line would realize the parts were flawed and that therefore, they would never be put into the planes:
I never though they'd install them .... I thought they'd stop 'em before anybody took off.
When Chris continues to press him about why he did it, Joe finally bursts out,
For you, a business for you!
Keller's dream is to pass his business to his son. He does not allow himself to truly imagine the consequences of what he has done, because doing so would put him in an impossible position, having to make a choice between his business and the lives of the pilots.