If I had access to some "magical" thing that everyone knew contained all truth beyond a shadow of a doubt, then of course I would believe whatever it said was true.
Of course, would it just provide a "yes" or "no" answer, or would it provide details? Some things are not black and white like the examples you provided. You can argue both sides of the example you provided (raise taxes on rich) b/c the issue is never as simple as just one thing happening. Would this magical thing have access to the future and see what the real outcome of things would be? You must understand that some people argue based on what they believe to be true and others just argue based on party politics... this being the case, some people really believe that what they hold to is what is best for the country and conflict with others who sincerely believe in the opposite thing and believe they know what is best for the country as well. Without an ability to see into the future, we really don't know what the best course of action is. The best answer might actually have worse results just due to other factors that come into play.. so without access to the future, we don't know what the best course of action is.
Of course, if the thing could see into the future, the answer might always be, "You are all screwed."