It's really simple, and it's the flip-side of the argument you've been making...
Objective information is that which remains unchanged when you change the observer to arbitrary but reasonable viewpoints.
What's 'reasonable'? It depends on the purpose of observation. If you don't know why you observe, you may have trouble deciding what's a reasonable viewpoint and therefore you can't decide what's objective.
One description of 'rational' is to know why you do what you do, not to wait for the results to tell you why you did what you did.
Can we at least agree that you've run aground here? This form of reasoning obviously doesn't work.
And it's not me alone whose been making this argument. This has been the one major elephant in the room for all science and philosophy throughout the 20'th century until today.
You might find "The Structure of Scientific Revolutions" by Thomas Kuhn interesting? It deals with just this problem within science, and what we can do about it. The book is also the most famous book on the topic...and I should add...among scientists.
http://www.amazon.com/dp/0226458083/?tag=absolutewritedm-20