Opinions on subjective things can't be wrong, because by their nature they only apply to the holder of the opinion, not the subject of the opinion itself. If I say "'x' is the greatest band of all time", what I'm really saying is that 'x' is the band whose music I find most enjoyable. Which is based on my tastes and experiences; the music I grew up with, the other music I've been exposed to, being dropped repeatedly as an infant, and so on. If I have a doctorate in music theory from a prestigous university, my opinion may have more weight with others, and I may have more convincing language at my disposal to convince others of the sound reasoning behind it, not to mention having a doctorate in my back pocket with which to smite the plebians for the stupidity of their divergent views. But the fact that band 'x' is made up of a kazoo, a bagpipe, and a theremin played by chimpanzees doesn't really change that I enjoy their music.
Now if I were to say, for example, that Barack Obama is both an atheist and a Muslim, I'm wrong by definition on objective, factual matters. And I'm an idiot. And no one should listen to me. And I should probably be hitting up Fox News for my own show.