Although butch–femme wasn't the only organizing principle among lesbians in the mid-20th century, it was particularly prominent in the working-class lesbian bar culture of the 1940s, '50s, and '60s, where butch–femme was the norm, while butch–butch and femme–femme relationships were taboo. Those who switched roles were called "ki-ki", a pejorative term, and they were often the butt of jokes. In the 1950s, in an early piece of lesbian studies, the gay rights campaigning organisation ONE, Inc. assigned Stella Rush to study "the butch/femme phenomenon" in gay bars. Rush reported that women held strong opinions, that "role distinctions needed to be sharply drawn," and that not being one or the other earned strong disapproval from both groups. It has been noted that, at least in part, kiki women were unwelcome where lesbians gathered because their apparent lack of understanding of the butch–femme dress code might indicate that they were policewomen. In contrast to ONE, Inc. studies, more conservative homophile organizations of the 1950s, such as the Daughters of Bilitis, discouraged butch-femme roles and identities. This was especially true in relation to the butch identity, as the organization held the belief that assimilation into heterosexual society was the goal of the homophile movement. Gender expressions outside of the norm prevented assimilation. In the 1970s, the development of lesbian feminism pushed butch-femme roles out of popularity. Lesbian separatists such as Sheila Jeffreys argued that all forms of masculinity, including masculine butch women, were negative and harmful to women. The group of radical lesbians often credited with sparking lesbian feminism, Radicalesbians, called butch culture “male-identified role-playing among lesbians”. This encouraged the emergence of androgyny in lesbian feminist circles, with many women wearing clothing like T-shirts, jeans, flannels, and boots. This dress was very similar to butch dress, weakening a key identifier of butch lesbians. While butch-femme roles had previously been the primary way of identifying lesbians and quantifying lesbian relationships in the 1940s, 50s, and 60s, lesbian feminist ideology had turned these roles into a "perversion of lesbian identity". Lesbian feminism was publicly represented though white feminism, and often excluded and alienated working class lesbians and lesbians of color. In these excluded communities, butch-femme roles persisted and grew throughout the 1970s.