Fair enough, but please tell them that before they enter a contract with you. Don't take their cash followed by not providing a service for reasons not stipulated before accepting the money.

You would think "please don't be an asshole" would be common sense, but I suppose adding it your product description about you providing support is being explicit.

Not only providing support, but unilaterally disabling the product they purchased after the fact. That should be incredibly explicit. And even then.

Just look at Ham Radio Deluxe.

This is actually not true if you hope to sell long term as an Amazon marketplace seller.

Is existing only at Amazon's pleasure any kind of long term strategy for a business?

Depends on what you mean by long-term. It seems to be working well enough for a significant number of businesses at the moment, and has been for some years now.

Nope.

If you've already sold them the product, you really cannot do this.

No? If I went into a store to complain and my first words were "what kind of shit have I bought here?", then I don't think I'd have any cause for complaint if I were forcibly ejected and told to come back when I'd learnt how to behave myself. Same should apply online.

If the store then came to your house and confiscated your product, you absolutely WOULD have the right to complain.

The store owner could go to jail, because that is called theft.

Screwing over customers has a cost.

This story went viral. And now this business is going to receive hundreds of negative reviews.

The product wasn't confiscated though, only the service was cancelled, and a refund was offered for returning the product. This is the main point a lot of people are missing here.

As it stands, this is how ANY court of law would see it as well.