Let's recall that Sanger's main concern is making sure women can choose when and if they become mothers and how many children they have. Midway through her speech, she characterizes mothers who cannot choose the conditions under which they bear children as "enslaved."

Worry, strain, shock, unhappiness, enforced maternity, may all poison the blood of the enslaved mother […] (41)

An—no real shocker here—a child born under those conditions ain't going to be living its best life.

In her final call to action, Sanger declares,

We want to free women from enslaved and unwilling motherhood. We are fighting for the emancipation of the mothers of the world, of the children of the world, and the children to be. (104-105)

There's no doubt about it: Sanger can be confusing. One moment she's talking in a really inhumane way about poor children acting as weeds…and the next she's saying truly revolutionary stuff like this.