I think that it is sad that we cannot intelligently discuss anything that has to do with group differences. Charles Murray's work in the Bell Curve might have had some methodological problems, but nothing deserving the vilification he received.

He has more recently written a nice piece arguing against the taboo against scholarship of this sort (link). Here is a short excerpt from it:

1. The differences I discuss involve means and distributions. In all cases, the variation within groups is greater than the variation between groups. On psychological and cognitive dimensions, some members of both sexes and all races fall everywhere along the range. One implication of this is that genius does not come in one color or sex, and neither does any other human ability. Another is that a few minutes of conversation with individuals you meet will tell you much more about them than their group membership does. <SNIP>
   
2. The concepts of "inferiority" and "superiority" are inappropriate to group comparisons. On most specific human attributes, it is possible to specify a continuum running from "low" to "high," but the results cannot be combined into a score running from "bad" to "good." What is the best score on a continuum measuring aggressiveness? What is the relative importance of verbal skills versus, say, compassion? Of spatial skills versus industriousness? The aggregate excellences and shortcomings of human groups do not lend themselves to simple comparisons. That is why the members of just about every group can so easily conclude that they are God's chosen people. All of us use the weighting system that favors our group's strengths.

It seems that much criticism of Murray's work, as well as that of others who bring up group differences, is based not on so much on the idea that it's untrue as on the idea that it's "wrong" to mention such matters. We value free expression and inquiry enough, however, that the critics don't feel free to say that openly, and thus make their attacks much more loaded and personal than the statements they are attacking would warrant.