You make a joke out of changing your mind, which seems to imply that you don't actually plan to change your mind because you're confident that the views you hold now are absolutely correct, and that this is never going to change. I don't know your biography, but this implies that you never had to change your mind from other beliefs to get to your current ones: if you had, you might be a bit more humble.
I pointed out that it didn't imply that at all. What I didn't point out is that his statement that I never had to change my mind is absurd. We come into this world tabula rasa and so the simple fact of learning changes our minds.
By the way, I don't think it makes sense to "plan to change your mind." If you're planning to change your mind, why plan? Why not just change it? I'm reminded of Obama saying his views on same-sex marriage were evolving. How would he know? If you have a view at one point in time and it's different from a past view, it makes sense to say that your views have evolved. But are evolving? Give me a break.
I promised, though, to mention some issues on which I really have changed my mind. Here are a few.
1. I've gone back and forth about open borders. I didn't think about it much until I had to deal with the Immigration and Naturalization Service in the 1970s. Then I became an open borders believer. It was partly based on the bad treatment I had received from INS and partly on my understanding of economics, specifically free trade, arbitrage, labor markets, etc. Then Milton Friedman's criticism of open borders in a country with a large welfare state gave me pause. Now I'm back to cautious support of open borders, based partly on Bryan Caplan's arguments--not just his but those by others that he haas made me aware of--and arguments by Alex Nowrasteh and Zac Gochenour.
2. I was a strong believer in the Cold War, that is, in the importance of having a strong NATO to offset the Soviet Union. The more I learned in the late 1970s and 1980s from Roy Childs and others, and in the 1990s and 2000s, the more I think that NATO was a mistake.
3. I was a mild supporter of the U.S. government's war on North Vietnam. I started thinking, shortly after moving to the United States in the early 1970s, that that was a huge mistake.
4. In large part due to the fact that I became a libertarian by reading Ayn Rand, I bought her view that we need government for police and courts. The more I read about how badly government does these things, the more strongly I believe that it would be hard for private provision of police and courts to do worse. Now, when I hear John Stossel say, as he often does, that we need government to run these things, I find myself actually wincing.
5. I grew up in English-speaking Canada as someone who thought Winston Churchill was a hero. Bit by bit, as I've learned more, I no longer have that view. Related to that, I think that it was wrong for the British and U.S. governments to ally with one of history's greatest mass murderers, Joseph Stalin.
6. I used to hate the left. I thought that when the Cato Institute started Inquiry magazine, they were selling out to the left. It was my friend, Roy Childs, who wrote me a stern 5-page letter chiding me for my ignorant attacks on Inquiry. After Roy died, I told some friends that I regarded that letter as a love letter because his taking time from a busy life to lay out just how and where I was wrong showed so much love for me. (Unfortunately, the letter burned in my 2007 fire.) I no longer hate the left. Actually, I don't hate anyone. I like some on the left and don't like others. I have allied with the left locally on antiwar issues and have met some really good people on the left.
7. I think the biggest issue I've changed on, and it happened in fits and starts from the late 1970s to now, is foreign policy. It's easy to see why U.S. participation in World War I was a bad idea. The one I believed from a very early age was U.S. and Canadian participation in World War II. I no longer think that was a good idea.
8. One issue I changed my mind on very quickly was how good a president Barack Obama would be. I had some hope for him in early 2008 and thought he masterfully handled Hillary Clinton, making a strong case in the Hollywood debate for not mandating that people buy health insurance. I also was glad to see him argue strongly against Bush's surveillance state. When he broke his word that he would filibuster a 2008 bill and actually voted for it, I knew he was a fraud. Having said that, I still think he's better than McCain would have been.
Those are a few for now.
What I notice in each case is that my views are affected by two things and almost entirely two things: evidence and logical argument.
I just remembered one other change in my thinking. I became a libertarian at age 17 and part of libertarianism is believing in the right to own guns. Intellectually, I was there. Emotionally, I was not. I had grown up in Canada and had picked up my father's intense fear of guns. But my emotions about it changed after I got more information. Specifically, I read Don Kates, ed., Handgun Control: The Liberal Skeptics Speak Out.