Sumo Power were not involved in the dealings with 'John', so they have nothing to answer for. They have an employment contract with 'Gary' which has no relevance to his previous activities, they employ the guy to do a job and as long as he has the capability to do that job the contract is being fulfilled. If the guy isn't allowed to keep a job and earn some money, there's even less chance that 'John' will ever see back anything he's owed.
This 'Gary' isn't running Sumo Power he now works for them, there's a big difference. Choose to avoid Sumo Power if you feel strongly enough, however just make sure you don't take your car to another GTaRt instead.