"Instead of just killing people, why not specifically target genetic disasters."

Wasn't that what was attempted in Poland 60+ years ago? Dig up all the intelligentsia and their children and massacre them? (My history-fu is wanting, so I may be wrong on this).

Of course, the only real impact that that seems to have had had is the creation of jokes about Polish people. I know plenty of smart people of Polish descent (of course, that may be because the ones that didn't get slaughtered fled to America).