In the early seventies, the GSS began tracking responses to questions about whether or not controversial characters should be allowed to speak publicly to advocate in favor of their eponymous interests. Since 1976, the survey has consistently queried respondents on five of them; atheists, homosexuals, militarists, communists, and racists. I wondered how public sentiment towards allowing members of these groups to push their messages in public had shifted over the course of the last four decades. The following graph shows as much:
The general trend overall has been that the majority, always in favor of free speech, has become even larger, the notable exception being for racists, for whom support has mostly moved along horizontally. As polite society declares both irrational racism and measured racialism (which are unfortunately mostly perceived to be synonymous phrases--both invoking images of tattooed, shouting neo-Nazis, not Jared Taylor) to be anathema, this isn't especially surprising.
With the folding of the Soviet Union and the ending of the Cold War, military juntas and communist dictatorships became history's vanquished. As the perceived threats they posed receded, tolerance for their ideas increased. In 2008, the most recent year in which the GSS has published data, a sixth speaker has been added. Only 41.5% of respondents say that an imam preaching hatred of the US should be allowed to speak. I suspect that tension between the West and the Muslim world is only going to grow in the foreseeable future, but if we do find the will to push most of them out while simultaneously losing interest in their sand holes, the number opposing such speech would probably decline as well.
It would be interesting to see the same trends measured over time for other western European countries. As effectively as the PC forces smother unapproved discourse in the US, I suspect public sentiment would be considerably less tolerant of the various speakers considered on the other side of the Atlantic than it is here.
GSS variables used: SPKRAC, SPKATH, SPKCOM, SPKMIL, SPKHOMO, SPKMSLM, YEAR