Why Even Your Mom Lies to You
People lie to you constantly in customer conversations, and mostly without malice. They want to be nice. They want you to go away happy. They don't want to crush your dream over coffee.
The lies get worse when you mention your idea, because now they know what answer makes you smile. 'Would you use this?' invites a polite yes that costs them nothing. Opinions are worthless. Predictions about future behavior ('I would definitely buy that') are worse than worthless because they feel like validation.
Fitzpatrick's fix: it's not their job to tell you the truth. It's your job to ask questions that make lying impossible. Facts about what someone already did can't be faked to spare your feelings.
Key idea
People lie to be nice, and mentioning your idea tells them which lie you want to hear. Ask about facts, not opinions, so honesty is the only option.