As for the notion that there’s merit to be found in stepping out of the arena to think great thoughts, I don’t get it. The most useful ideas emerge from engagement with the world, not withdrawal from it.
It is tempting to say, “Of course you don’t get it–you think the criterion for measuring the worth of ideas is their utility,” but that would not be sufficient. As Stuttaford presumably knows, it was during their time in “the wilderness” that the Tories did some of their best policy thinking and laid the groundwork for what followed in the 1980s, and the same could be said, perhaps to a lesser extent, about conservatives here during the same period. There is also something very strange in thinking that going into the political wilderness has something to do with living the life of an anchorite, as if the entirety of “the world” was the government and the political process. Is it unimaginable that one could “engage” the world without being bogged down in the minutiae of party politics for a few years?
P.S. This line of criticism is very similar to the sort of thing you hear from people who belittle liberal arts students: “What are you going to do with that?” Oh, I don’t know, perhaps understand something of lasting value?
Update: Stuttaford  has responded, and from his second post I see that I read too much into his original comment about “engagement with the world”:
Unfortunately he seems to overlook the fact (or I didn’t make it sufficiently clear) that what I was writing about was politics, nothing more, nothing less.
Fair enough. I also take his point that the policy work that prepared the way for Thatcher’s government had been going on before the Tories had been in the political wilderness. It seems to me that he and McArdle  are basically in agreement, and when McArdle talks about “going into the wilderness for a little while, where they can get their heads together without having to worry about the intellectual compromises of actual politics,” this is not an abandonment of “the business of shaping policy and winning elections.” I would say that it is instead a necessary precondition to that business, and that a period of time in opposition may make your arguments sharper and better attuned to changing circumstances.