<perhaps the use of the word "stupid" in written english is somewhat different from its italian use, so i may be wrong.....nonetheless i think i can feel offended in some way, can't ?>
When the current US president, Bill Clinton, was first running for office, his campaign staff had a motto to remind them about what was important to the public and therefore made them more likely to vote for Mr. Clinton. That motto was 'It's the economy, stupid!'
Means talk about what people care about, not what bores or annoys them.
Mr. King was making a reference which would be well known to his US readers, but naturally not as well known outside this country.
He certainly was not trying to offend you, I'm certain.
Your English is good, and as with Mr. Brochu's observation about laws governing fossil excavation earlier, it's worthwile for you to point out when people are being insular.