Answer: Stupid question from a dumb marketing person.
Marketing isn't about CHANGING someone's opinion. Marketing is about finding people that want something and then crafting your message/telling a story to fit in with their worldview.
Let me quote Seth Godin in his book, All Marketers Tell Stories:
"Don't try to use facts to prove your case and to insist that people change their biases. You don't have enough time and you don't have enough money."
His point is that people already have formed a worldview and they tell themselves stories to support that worldview. Your job as a marketer, according to Godin:
"...identify a population with a certain worldview, frame your story in terms of that worldview and you win."
If you are spending all your marketing money, budget, resources, and time attempting to convince people to change their opinion about something, you are going to fail. There isn't enough time and there isn't enough money in anyone's budget to change people's opinions.
If you haven't done this already, be sure to visit Seth Godin's blog on a regular basis. It might save you some time and money.