Secret to winning an argument is ridiculously simple

If you want to change someone's opinion, ask them how they would do something instead of why.
The insight comes from University of Colorado psychologist Philip M. Fernbach in a paper with the telling title "Political Extremism Is Supported by an Illusion of Understanding."
His theory: Political extremists might be a touch less extreme if they had to explain just how their favored policy would create the changes they sought, as opposed to listing off the reasons that they're right.
For the experiment, Fernbach asked two groups of online participants to give their opinions on a variety of controversial and complex policy issues, such as healthcare.
Mind Hacks detailed the experiment:
One group was asked to give their opinion and then provide reasons for why they held that view. This group got the opportunity to put their side of the issue, in the same way anyone in an argument or debate has a chance to argue their case.
Those in the second group did something subtly different. Rather than provide reasons, they were asked to explain how the policy they were advocating would work. They were asked to trace, step by step, from start to finish, the causal path from the policy to the effects it was supposed to have.
The results were striking.
In line with Fernbach's hypothesis, folks who gave their reasons for being right were just as convinced of their convictions after the experiment as they were beforehand.
But the people who had to explain the mechanics of implementation had suddenly softer views. Not only that — they also gave themselves a lower rating on their understanding of the subject.
The two takeaways:
If you want to win an argument, ask your friend/colleague/partner/nemesis to explain how their perspective can be brought into reality.
If you want to remain convinced of your position, don't just bring your reasons for why you're right to the debate — make sure to bring along implementations too.
But this kind of rhetorical humility is more rare than you think. "Freakonomics" coauthor and University of Chicago psychologist Steven Levitt told us that in all of the consulting he's done, one pattern is clear: "Businesspeople, especially in front of their bosses, have an almost unlimited ability to sit back and mint answers they don't know."