From 1989 to 1996 the position was that immigration should be "stabilized"- i.e. reduced to the level where the entire US's population does not grow. In 1996 the position was changed to neutrality; from 1998 to the present the club has been split on whether or not to oppose immigration (with the majority favoring neutrality).
A response essay written by Eliezer Yudkowsky posted at Cato Unbound for the issue Brain, Belief, and Politics:
Is That Your True Rejection? by Eliezer Yudkowsky
The lead essay has been written by Michael Shermer:
Liberty and Science by Michael Shermer