If you believe Eliezer, then you may believe him that the basilisk has ~0 probability of occurring. (I should find a citation for that, but I read it just a few minutes ago, somewhere around the discussion of this xkcd comic.) So you are already protected from it, because it does not exist (not even in ways relevant to acausal trade). More broadly, you should decide to take this approach: never give into blackmail by somebody who knows that you have decided to take this approach. Now they have no incentive to blackmail you, and you are safe, even if they do exist! (I think that the strategy in this paragraph has been endorsed by Eliezer, but don't trust me on that until you get a citation. Until then, you'll have to reason it out for yourself.)