Wish people would do basic fact checks. While Sanger indeed gave a speech in front of women's branch of KKK, she did not describe it favorably. At the time, she was giving birth control speeches in front of any group of people willing to listen.
This particular speech was no secret. It was well documented by Sanger herself and well known for decades; she talked openly about it, and had no favorable words describing the audience. Regardless her speech in front of the KKK audience, leaders of 60's civil right movement (including Dr. Martin Luther King, Jr. himself) spoke of her favorably; fully aware that she did gave that speech, after all it was well known fact about her at the time.
There are no known photographs of the event. All the photographs circulating on the Internet showing her with white hooded man are fabrications; originals are easily traceable and none has Sanger in it. In reality, the audience were women, more than likely in plain clothing of that era. Even if there was genuine photograph of the event, it would most likely be impossible to tell from it that it was KKK event.
Some more info at http://www.snopes.com/margaret-sanger-kkk/
"""In 1926, Sanger gave a lecture on birth control to the women's auxiliary of the Ku Klux Klan in Silver Lake, New Jersey. She described it as "one of the weirdest experiences I had in lecturing," and added that she had to use only "the most elementary terms, as though I were trying to make children understand."""