Many, many things. In a nutshell, eugenics took darwinism too far and preached selective breeding for humans. In the context of the era (right before WWII in fact, there's a nice give-away) that simply meant that people deemed 'undersirable' by the governing class should be removed from the gene pool. This included disabled people, criminals, pretty much anyone who wasn't white, but also the poor, because in those days the idea was that the poor were poor because they were not capable of hard work and lacked the qualities a decent human being should have. Fanatic eugenicists (or whetever they're called in English) wanted to sterelize huge chuncks of the population. This actually happened to the black population in th US for a short while. And the there was that nasty little Austrian dude, name escapes me at the moment, something with a pure race and a bunker...
So, you know, if you really feel there's nothing wrong with that, I really can't help you.
http://en.wikipedia....iberal_eugenics
Your argument is pretty odd. If every political belief/religious belief were to be dismissed because some people took it too far then there'd be nothing left