In contemporary Western society it is widely believed that sexual behavior is evaluated differently depending on whether a man or a woman engages in it (Milhausen & Herold, 2001). This view, known as the sexual double standard, suggests that for men, sexual behavior brings praise and respect, whereas for women, identical sexual behavior brings derogation and disrepute. Although the general public’s belief in the sexual double standard is pervasive, (Marks, 2002; Milhausen & Herold, 1999), the research literature paints a different picture. Person perception studies, which feature men and women engaged in identical levels of sexual activity, are widely used to assess how sexual behavior is evaluated depending on the sex of the person engaging in it. To date, these studies show limited empirical support for the double standard (e.g., Gentry, 1998; Jacoby & Williams, 1985; Mark & Miller, 1986; Marks & Fraley, 2005a; Oliver & Sedikides, 1992; O’Sullivan, 1995; Sprecher, 1989; Sprecher, McKinney, Walsh, & Anderson, 1988). These ﬁndings are surprising considering the preponderance of anecdotal evidence for the existence of a double standard. [...]
Although the sexual double standard seems selfevident, person perception studies generally fail to show that people actually evaluate sexually active men and women differently. For example, Gentry (1998) conducted a person perception task in which participants evaluated male and female targets with varied levels of sexual experience. Evaluations were based on level of sexual experience and relationship type (casual or committed), but not on target gender. O’Sullivan (1995) followed a similar protocol and found that targets were rated based on the amount of sexual experience they reported, but ratings did not vary as a function of target gender. We (Marks & Fraley, 2005a) conducted a person perception study designed to rectify some methodological concerns of previous double standard studies, yet we found little evidence of a double standard.
Although some researchers have reported evidence of a double standard, comparable ﬁndings frequently fail to emerge in later studies. For instance, Sprecher, McKinney, and Orbuch (1987) conducted a person perception study and found evidence of a double standard that was conditional on age and the context (committed or casual) in which the loss of virginity occurred. However, data from other studies have failed to corroborate either the age effect (Sprecher, 1989; Sprecher et al., 1988) or the context effect (O’Sullivan, 1995). In summary, although it appears that people do evaluate others according to the amount of sexual activity they report, person perception research rarely shows that people evaluate men and women differently as a function of their sexual activity. Even when an interaction between target gender and sexual activity has been found, it is often found only in highly circumscribed situations (see Crawford & Popp, 2003, for a review). If the sexual double standard is as pervasive and powerful as many people believe, empirical evidence for its role in person evaluation should be less elusive. - from here
There is more to that. Apparently, part of the reason many people believe in that double standard is confirmation bias.
In contemporary Western societies it is widely believed that there is a sexual double standard such that men are rewarded for sexual activity, whereas women are derogated for sexual activity. This pervasive belief may result in a conﬁrmation bias such that people tend to notice information that conﬁrms the double standard and fail to notice information that refutes it. Two studies were conducted to test this hypothesis. In both studies, participants read vignettes about a target man or a woman that contained an equal number of positive and negative comments regarding the target’s sexuality. Participants recalled more information consistent with the double standard than inconsistent with it.