Re: The science of Economics
Your argument applies equally, if not more strongly, to paleontology. That's usually granted scientific status. Likewise, a lot of medical knowledge has been learned by observing things that would never pass an ethics committee, but which happened anyway.
You can interpret an experiment that someone else performed, without even knowing the original design or intentions. As long as you know what the experiment actually involved and what the results actually were, you can still use those results to test hypotheses that you bring to the party after the experiment has "finished".