In other words, when we consider groups that most people discriminate against, and feel they are justified in doing so, disparaging humor towards that group does not foster discriminatory acts against them. On the other hand, for groups for whom the prejudice norm is shifting, and there is still no consensus not to discriminated against (women, gays, Muslims and so on), if you hold negative views against one of these groups, hearing disparaging jokes about them "releases" inhibitions you might have, and you feel it's ok to discriminate against them.
Previous studies by Ford and others on sexist humor showed the same pattern. People who are sexist to begin with and enjoy sexist jokes show higher tolerance for sexist events, tend to accept rape myths, and tend to show greater willingness to discriminate against women.
These studies illuminate some aspects of humor that people sometimes tend to ignore. First, humor depends largely on the context and on the personality and the attitudes of the audience