[afarrell]

The problem is that "normal" has two meanings:

1) common

2) according to social norms

Neither of which are actually the same as ethics.

I'll make a slightly stronger argument though. You should do business with those you trust. There is no rigorous rational way to determine someone's trustworthiness, so you must get to know them and see how they respond to situations and ultimately rely on your intuition for making decisions.