I look on people like this with pity. For them, money is an addiction. They'll do anything for their fix. They'll lie, cheat, steal. Those aren't the kinds of people to do business with, because eventually they'll look to get their fix from you.
Business is about profit, not feeling good about the people you buy/sell services from/to.
Defend yourself if you see a need. Don't avoid people just because you don't get a warm feeling when you exchange services with them.
I've refused to create accounts for other types of individuals on more than one occasion. If they want to use a competing product, that's okay with me. I don't mind losing business from customers I don't appreciate. If someone is a nasty person I don't want them to benefit from the use of my product. Check out some of the firing bad clients threads. Best just not to do business with them in the first place.
It's my little way to shape my world and surround myself with people I appreciate -- that's more important to me than money.