1. I think Milton Friedman felt defensive about his libertarian activism. The main reason, I think, was the attitude of his close friend, George Stigler, who HATED activism. I remember at the Mont Pelerin Society meeting in Hong Kong, when I asked Hayek a question after he had suggested a grand debate between proponents of free markets and proponents of socialism. Hayek had said that the debate should be on the issue "Resolved that coercion is the best way to run an economy," or words to that effect. I stood up and suggested to Hayek that the issue should be stated more neutrally because the danger was that socialists would not accept that the difference between them and free marketeers was a belief in coercion. Hayek said he would consider it. After the session ended, Stigler came up to me and said, with a putdown tone, "Hayek is an actionist." "Actionist" was his word for "activist." Stigler thought he had found a kindred spirit in me. (This was after his presidential address the night before, when he had told us that there was no point in telling politicians, or voters, for that matter, anything because they already knew it.) I told Stigler that I was an activist also but that I wanted the activism to be effective. Stigler harumphed.
Think about Milton and Rose's book, Free to Choose. What was the subtitle? "A Personal Statement." Read through the book and, excellent as it is, there is virtually nothing personal about it. So why did Milton and Rose title it that? I think it was because Milton felt defensive with arguably his best friend putting him down for "actionism." So Milton compromised by saying, in effect, "George, let me have my avocation."
2. I remember reading an interview with Milton in the 1990s in which one sentence shocked me. I think it was in the San Francisco Chronicle. Milton was talking about what it was like to be retired and focusing on public policy activism rather than scholarly research. Milton said that it was easier to "sling the bull." In anything I ever read, heard, or saw Milton say, I would never accuse him of "slinging the bull." So why did he say it? I think he had internalized the idea that public policy activism was not serious in the way scholarship is. This is common, by the way. I've had a couple of economist friends ask me "So have you been doing any serious work lately." My friend Bob Barro has done this, for example. I answer, "All of my work is serious."