Breaking the nose of someone and running is normally criminal. But if you're breaking the nose of someone and running to avoid a flash kidnapping, that's perfectly justifiable.
Disrespecting a contract is normally criminal. Disrespecting a contract to avoid the other party to steal from you is normally justifiable (unless of course the breach of contract implies you taking much more from the other party than what this party is taking from you, i.e., disproportional reaction).
The main mistake of Roger here was being too impulsive. Perhaps the customer was innocent. So maybe the best action on Roger's part was to only act after some mediation decided he's right - he had the time to do so anyway. On the other hand, professional mediation would likely cost much more than 5BTC. And he was convinced the guy was a liar. If he's really correct, his actions would be justifiable in comparison to the actions of Nethead.
Anyway, it wouldn't hurt to state what you say in the TOS - that they have the right to break their contract with you if you steal from them is something that's ethically deductible anyway, explicitly stating it would help making it clearer.
The issue in this event was that nobody was stealing from blockchain.info. blockchain.info was not due any funds. Roger, acting in an employee capacity at blockchain.info abused his access to their database to violate blockchain.info's privacy policy so as to gain leverage in a dispute between BitcoinStore.com and a BitcoinStore.com customer.
If Roger had violated BitcoinStore.com's privacy policy and publicly used personal information stored by BitcoinStore.com in an attempt to resolve what he believed to be a fraudulent action, it would have been less severe (I still hold that it would have been wrong of him, but not as bad as what he did). Instead, information that only blockchain.info was supposed to have was revealed to BitcoinStore.com to assist them in their investigation and their attempt to determine whether fraud had even occured.
Are you arguing that I should be able to contact blockchain.info and ask them for a list of all bitcoin addresses associated with your email address or phone number so I can check and see if you have engaged in fraud with me? Even if it violates blockchain.info's privacy policy?
How is blockchain.info supposed to know if I have a valid fraud claim against you or am just fishing for information I can use to blackmail you?