Not long ago, I got a sales letter that -- while extremely well written and was selling a very high-quality product -- committed a truly stupid marketing mistake.

A mistake that probably cost the company running the ad a TON of money in lost sales.

What was this mistake?

This: In order to make a point, he blatantly insulted the "Intelligent Design" movement. Saying people who believed it were misguided and not too "intelligent."

Okay so what?

Here's what: At this time, this debate -- no matter what side you are on -- is erupting around the U.S. And if you look at any poll, you will see at least half the people in the U.S. -- and even a good chunk of people in more secular countries, like the United Kingdom -- don't believe in random evolution.

Which means, unless he was writing to atheists, humanists or other people who do not believe in intelligent design (he was writing to people who are interested in making money -- which spans almost every group of people), he automatically turned away people who disagree with him, by violating their established belief systems. And in the process, murdered a good portion of his own sales.

Why?

Because when you say something that violates someone's core beliefs -- whether you're right or wrong -- instead of looking for reasons to buy from you, people will start to look for reasons NOT to buy from you. Even if they want what you have, and even if they need it.

That doesn't mean you will lose everyone. But you will almost always lose people (maybe even a lot of people) who would otherwise have bought from you. And these lost sales can add up real fast.

Hollywood is finally catching on to this. Films and TV shows that star the more "outspoken" actors -- especially the ones who used to bring in tens of millions of moviegoers -- are now flopping left and right. Even if the movie is good, and even with tons of publicity and "awards".

On the other hand -- and again, Hollywood is finally learning this lesson -- if you say things that reinforce and agree with your customer's beliefs, then they will be more willing to hear you out and listen.

Ben Settle is an expert copywriter and direct marketer. If you liked this article then check out Ben's website at http://bensettle.com -- and get your hands on over 500 pages of advertising ideas, strategies and tactics just like this one -- as well as rare swipe file ads and hot marketing information not easily found anywhere else.