"The research indicates that people should be aware of the prevalence of disparaging humor in popular culture, and that the guise of benign amusement or “it’s just a joke” gives it the potential to be a powerful and widespread force that can legitimize prejudice in our society, he said."
The actual study can be found here:
"A thousand bawdy, or even blasphemous, jokes do not help towards a man’s damnation so much as his discovery that almost anything he wants to do can be done, not only without disapproval but with the admiration of his fellows, if only it can get itself treated as a joke." —C. S. Lewis (1942)
"Sexist humor—the denigration of women through humor—for instance, trivializes sex discrimination under the veil of benign amusement, thus precluding challenges or opposition that nonhumorous sexist communication would likely incur."
"...sexist humor is not simply benign amusement, that it can affect men’s perception of the immediate social context and thus promote behavioral expressions of sexism without fears of disapproval of their “fellows.” Specifically, we propose that sexist humor acts as a “releaser” of prejudice, that is, for men who have antagonistic attitudes toward women, sexist humor allows them to express their sexism by replacing the usual nonsexist norms in a situation with a norm of tolerance of sex discrimination. Sexist humor essentially justifies a wider range of negative responses toward women. In this climate tolerant of derision, sexist behavior can be more easily justified as falling within the bounds of social acceptability."