Ok, well, assuming you make a choice to try and achieve something, yes? And you make that choice based on the information available to you. If that information is false, then whatever your choice was, you could not achieve the desired effect (save by lucky coincidence, which we can ignore).
So if your decision is based on a false assumption, this supposition goes, does the choice not then become worthless? It cannot achieve its purpose- to achieve the desired effect. Whatever achieves might be significant in other ways but the choice itself is invalid.