PETA (People for the Ethical Treatment of Animals) often uses sexualized imagery in order to help promote awareness for animal rights. (the image used in this article is mild in comparison)
Such uses of sexualized imagery are also found in other ethical campaigns, such as feminist protests.
A wide range of research shows that women (and sometimes men) are perceived more negatively when people focus solely on their physical appearance, or when the women are dressed in more provacative clothing. Specifically, they are perceived as less intelligent, moral and kind, and even are perceived to have fewer thoughts. Women when sexualized are also perceived as more animalistic. This extends to moral concern as well; sexualized women are perceived to suffer less when they are raped or sexually harassed, and are blamed more when these atrocities occur.
Recent research tested if sexualized imagery of women is beneficial or harmful in promoting ethical causes, specifically, in relation to PETA.
The results indicated that people showed less support for PETA, and had reduced intentions to behave in ways that are consistent with PETA's mission, when images of sexualized women were used to promote the cause. Interestingly, this was found to occur because the women in the images were dehumanized (likened more to animals). In other words, people perceived the women more negatively when sexualized, and for whatever reason, because of this, people showed less support for PETA.
Sex sells, except when it comes to ethical causes.