It seems safe to say that a substantial portion of respondents were not readers of Liberty at that time. But the most important reason, I believe, is not intellectual at all. And dialogue is commonly necessary to change people's minds. For this reason, libertarianism deduced from the non-aggression imperative does poorly in the intellectual arena. In fact, it is usually counterproductive, and libertarians are finding that out.
Moralistic libertarianism offers a pretty easy answer to just about any kind of policy question.
If a government policy involves the initiation of force, it's bad. If it doesn't, it's permissible. For the moralistic libertarian, the non-aggression imperative is a sort of trump card. Invoking the non-aggression imperative in argument with other libertarians very often wins arguments with those who agree with it. But unfortunately, as those of us who have cited it in discussion with non-libertarians are well aware, a lot of people find it unconvincing.