The best way to fight this would not to block them, that does not cause Amazon/others anything. (clearly).

What if instead it was possible to feed the bots clearly damaging and harmfull content?

If done on a larger scale, and Amazon discovers the poisoned pills they could have to spend money rooting it out, quick like, and make attempts to stop their bots to ingest it.

Of course nobody wants to have that tuff on their own site though. That is the biggest problem with this.