I also support these ideas on principle, but in practise it's just not as simple.
I was born to a paranoid schizophreniac (delusional, manic depressive, responsibility averse whore), and a druggy surfer who hasn't worked in thirty years. By rights, both myself and my sister should be utterly useless.
Only it didn't work out that way. Both of us have IQs over 160 (unmeasurable in both instances because of perfect scores in specific areas), topped our respective schools, form meaningful, stable relationships and are training to become professionals.
We were removed from our single mother's care at 14 and 7 respectively - prior to that we basically didn't attend school.
The problem with any system of eugenics is that there will be exceptions to your rule, and society benefits from having exceptions both in this sense, and in the sense of base genetic variation. By instigating sterilisation according to the ability of a person to fit into a society, you aren't making the society funciton better so much as you are ensuring that the society will always remain in it's current form.
You also assume that your traits aren't desirable.
http://en.wikipedia.org/wiki/Monoamine_oxidase#Genetics
http://www.sciencemag.org/cgi/content/summary/297/5582/752a
|> Violent, antisocial behaviour is just about the only thing that ever motivates short term political change. Without people acting like this, society loses it's ability to react quickly to trends that don't benefit it. If everyone is a well adjusted individual, no one will be the one to instigate reactionary movements. Stagnation will follow.
http://www.nature.com/news/2008/080404/full/news.2008.738.html
|> is likely a vital factor in the success of market economics.
http://www.nature.com/news/2004/040809/full/news040809-10.html
|> Laziness isn't necessarily undesirable. Having a lazy sector of society ensures that industrial relations have a baseline to offset workoholics' influence. Which is a good thing. Fuck you if you dare say I should work more :).
The point at which we mandate which psychological traits are desirable and which aren't is the point at which we cross the line. That is where are altering what society itself will be, and what it will value. That is where the system begins to feed into itself.
Now euthanising people who can't contribute to ANY concievable society in any concievable way (down syndrome, vegetables, being two examples) is a whole seperate kettle of fish which I'd love to shoot in a barrel.