I did an Ctrl-F to find the word “youngest” in that link and it is not there.
Could you direct me to the quote?
http://www.bartleby.com/1013/5.html
It doesn't match the wording exactly as given by Wagglebee, which may be why netmilsmom didn't find it in a search of the page. Wagglebee gave the quote as The kindest thing that a large family can do for its youngest member is to kill it. In Lorianne's link, the quote is " The most merciful thing that the large family does to one of its infant members is to kill it."
Here it is in context:
10 Many, perhaps, will think it idle to go farther in demonstrating the immorality of large families, but since there is still an abundance of proof at hand, it may be offered for the sake of those who find difficulty in adjusting old-fashioned ideas to the facts. The most merciful thing that the large family does to one of its infant members is to kill it. The same factors which create the terrible infant mortality rate, and which swell the death rate of children between the ages of one and five, operate even more extensively to lower the health rate of the surviving members. Moreover, the overcrowded homes of large families reared in poverty further contribute to this condition. Lack of medical attention is still another factor, so that the child who must struggle for health in competition with other members of a closely packed family has still great difficulties to meet after its poor constitution and malnutrition have been accounted for.
Obviously, Wagglebee didn't distort the context at all. Sanger said what she said. And I believe she meant it.