This sounds remarkably like the beginnings of genetic counceling, as opposed to eugenics. Individuals with genetic diseases such as Huntington's disease, Tay-Sachs, hemophilia, cystic fibrosis and sickle-cell anemia probably shouldn't reporduce unless they wish to pass on these diseases.
We civilised men, on the other hand, do our utmost to check the process of elimination...
But this is true, we do have a proliferation of genetic diseases as a result of our compassion. Fortunately, medical research continues, and perhaps one day these horrible afflictions will be eliminated. Until then, I am glad genetic counseling is available as a direct result of studies in natural selection.
Just to add to Scully's excellent comments, Darwin was insightful enough to realize that the laws of inheritance might shed a new light on this issue. Negative selection, or culling of human disease used to be a goal until it was realized that rare diseases are so because they are genetically non-dominant. Such diseases would take hundreds of generations to weed out of the population by selective breeding. There may come a time when negative selection is possible again--if all the possible needles in the haystack are found by genetic testing and treatment or by preventing everybody from having children. So, only the aggregious, already expressed diseases in families with multiple diseased alleles can deliberately not be passed on.
Not to me, he clearly wants legislation to keep some from marrying. Having gotten rid of the Lord, he wants to play god. In the other quotes he also clearly wishes destruction of the frail and weak, war to destroy inferior races and many more despicable things. Clearly Darwin was a very despicable human being, a profound atheist, and his ethos is deeply imbedded in his philosophy.