TL;DR: Men make sexist and homophobic jokes to bond with men, and they care about other men’s reactions. The effects on women and others are explained in the article.
The male participants were not influenced by whether or not a woman objected to sexist jokes. They were, however, highly sensitive to how they thought another man would react to them, reducing their use of sexist jokes if they thought a man would be object.
What these results show is these jokes appear to have a “male bonding” function – that, primarily, men make such jokes typically to impress other men. Other research has suggested a similar function for homophobic slurs.