The only thing worse than a person with a spotty moral legacy is instances in which alleged contemporary critics pretend to be outraged about said legacy only because it helps to advance their extreme ideological views concerning contemporary issues and institutions -- issues which have nothing at all to do with the historical figure in question. This becomes especially problematic when such critics seem to know nothing more about the figure than that which they've been programmed to repeat, vomiting up criticisms without the benefit of historical knowledge.
Often, faux outrage is worse than no outrage, and worse still when the outrage is manufactured solely to promote (and persuade others to accept) an extreme view based on emotion, disinformation and ignorance rather than reason.
It's absurd and intellectually bankrupt to try and write history as though it were simple, monochromatic, or devoid of context, yet the pro-life crowd proudly embraces this tactic. Margaret Sanger's legacy isn't as easily summed up as those who suddenly find use for her would like, even if it is unquestionably flawed:
Sanger saw birth control as a means to prevent "dysgenic" children from being born into a disadvantaged life, and dismissed "positive eugenics" (which promoted greater fertility for the "fitter" upper classes) as impractical. Though many leaders in the eugenics movement were calling for active euthanasia of the "unfit," Sanger spoke out against such methods. She believed that women with the power and knowledge of birth control were in the best position to produce "fit" children." SOURCE
When Nazi Germany adopted the principles of eugenics to create a Germanic "master race," Sanger wrote in a letter:
"All the news from Germany is sad & horrible, and to me more dangerous than any other war going on any where because it has so many good people who applaud the atrocities & claim its right. The sudden antagonism in Germany against the Jews & the vitriolic hatred of them is spreading underground here & is far more dangerous than the aggressive policy of the Japanese in Manchuria.." SOURCE
Surrounding paragraphs certainly paint an unsettling picture of Sanger's racism through ignorance. Some of her views were morally flawed even without the benefit of ignorance. Still, the truth paints a more complex picture than the pro-life crowd could ever conceive or create via their simplistic palette.
There may be a lot of reasons to object to any positive, contemporary usage of Sanger's name, but those reasons shouldn't come from a crowd that cares more about their anti-choice agenda than they do about Sanger's historical flaws.