"The customer is always right" is a good mindset for both B2C and, to a lesser extent, B2B; but it should not be taken literally. If a customer in store is abusive, politely but firmly showing him the door is the right response. Do not deal with bad customers. But attacking a bad customer, stealing his stuff, etc. is a really bad idea.

Disabling a previously bought product for a negative review is probably illegal in most jurisdictions. It is clearly illegal under Amazon ToS. If I were the device buyer I would just return the unit. Even if they restore access this is an accident waiting to happen.

Reading this reinforced my conviction that I do not want my home hardware managed remotely. At least not the stuff I regularly interface with.