There’s a fascinating new study by Lee Epstein of the USC Law School that looks at how justices voted on free speech cases from 1953 to 2010. It shows that all justices are more likely to uphold the legality of speech that agrees with them ideologically, the conservatives on the court are far more likely than the liberals to do so. Here’s a chart showing how the most recent long-serving justices voted in such cases:
Note that the gap between how conservatives vote when liberal speech is at issue and how liberals vote when conservative speech is at issue is much, much larger. None of the four most liberal justices here have a gap of more than 16 points; none of the four most conservative justices have a gap of less than 42 points. The in-group bias of the conservative justices is far more prevalent and they are much more likely to support only speech that they agree with.
One might chalk that up to the fact that the liberal justices are just more supportive of free speech in the abstract and that’s clearly true. All of them voted to uphold the right to express conservative views at least 40% of the time. But that wouldn’t explain why all of the conservative justices supported the expression of conservative views at least 53% of the time and none of them supported the expression of liberal views more than 23% of the time. That gap is really quite staggering even with our understanding of in-group bias.