Rational [chat]-Interest

Mom:  I don't like shopping at Wal-Mart, but the prices are so much cheaper.  How can I not shop there?

Me:  Well, you recognize that the prices are lower as a result of their exploiting human beings.  For example, they deny most of their employees health insurance, and so increase suffering.  So, you shop other places in order to decrease your contribution to human suffering.

Mom:  And we need to spread money around, because if Wal-Mart doesn't have any competition their prices will go up!

Me:  ...well, yes.  There's that, too.