Ergh. An opinion is a subjective belief. It cannot be wrong. If someone says "I think Australia sucks because they invaded China" the statement that Australia invaded China is wrong, but their opinion isn't. Likewise, if someone else said "Australia is great because they hand out genetically engineered sex-slaves", their statement that Australia hands out genetically engineered sex-slaves is wrong, but their opinion isn't. If after finding out that's wrong they no longer think Australia is great and starts to think it sucks, neither their former or current opinion is wrong. They merely exchanged it for a new one.
Seriously, an opinion is like a group membership. You either have it or you don't. There is no wrong. Also, just because one part of a statement is wrong, doesn't make all parts of it wrong, and just because someone calls something an opinion, doesn't mean it is. Calling a false statement an opinion doesn't make it one. If someone says "In my opinion bacon is made from turtles" their opinion is not wrong because there is no opinion. It's a statement, and that statement is wrong.