“To build up an informed opinion is a matter of some difficulty: not in the opinion part of it, because the public frequently shows itself very opinionated on the slenderest of information. The difficulty rather lies in making sure the opinion is well-informed.”
Postscript: I could have sworn that it was the late-lamented football manager Brian Clough who said to his namesake commentator, Brian Moore: “Let’s face it Brian, we’re all entitled to our opinions, but it’s my opinion that counts”, however, I can’t find any reference to it! On reflection it seems that one of the most memorable quotes from my teens was simply a conceit of the TV impressionist Mike Yarwood.