Morally and ethically an opinion can sometimes be wrong. A pirate downloading all his music, movies and software thinks it's OK. He has right to have that opinion, but because it's clearly illegal, it's also morally and ethically wrong. However, this does not mean the criminal in question does not have right to think as he does; one cornerstone of a free world is that everybody has the right to have an opinion in everything.
In a free society, I can think whatever I prefer, form opinions not based on facts but on feelings. In my opinion my wife is the absolutely most beautiful and sexy person ever lived in this world. I honestly believe that, but I bet you have another opinion. I know I'm right in this but because I understand that you as a free person have the same right to have an opinion as I do, I have to accept that yours differs from mine, that in your opinion my opinion is wrong.