I quite dislike the word prove - it makes no sense. There is very little that we can know absolutely - apparently we can't even know that we exist (not quite sure how this was shown, but I believe Nietzsche showed it). Admittedly, this is taking skepticism to its extreme, but even things like science... There is a reason why it is called the THEORY of gravitation. What facts we chose to accept or not is generally somewhat subjective.
Also, if we stop arguing about subjective things, we will be robots. Humans are entirely subjective creatures - objectivity does not exist.