The Holocaust was "allowed" to happen for the same reason that gangs, violent crime, and road rage are allowed to happen, today:
1) "Decent" people are too afraid, powerless, or unwilling to act (i.e., it's always someone else's problem). Speeches are made, but people either listen with a deaf ear, or actually comprehend the vitriole, but assume that someone else will stop the lunatic.
2) Laws protect the guilty more than the innocent or victims (which media darling, today, will get a slap-on-the-wrist for abusing drugs?). Furthermore, revolving door prisons do nothing to rehabilitate prisoners, and practically foster the notion of "learning to become a better criminal"; IMHO, "lifers" and recidivists are a waste of space, and should be executed to save the police and courts time and effort, if not taxpayer money (for those of you who just want, "Tsk!", watch some of the documentaries on the "inside" of our jail system; it has failed, miserably, and the only solution is a radical one. And, please, spare me the dubious comparison between me wanting to annhiliate criminals versus Hitler's death camps, which were targeted at innocents-made-scapegoats; and, for the record, I also believe that violent and drug-dealing gangs should be exterminated off the face of the Earth, as well; they are no better than cockroaches, unworthy of a "second" chance).
3) Police are powerless to act unless they actually witness a crime occurring (unless they can piece it together from obvious clues and evidence, which could take hours, days, weeks, months, and sometimes even years!). Eventually, the criminals "win", so, in essence, crime becomes law. Likewise, the code of the military states that whoever is in power rules, even if that power is obviously evil, and may end up destroying that very same military (did you know that Saddam never allowed his military advisors (or anyone else, for that matter) to carry sidearms in his vicinity? can you guess why?).
Granted, all this makes the war on Iraq seem "appropriate", since Saddam had been in the process of killing thousands of his own people, but then, where is the "swift sword of justice" or "enduring freedom" against the same atrocities occurring in the rest of the world, right now, most notably in Africa?
'Nuff said?
Make sure you attribute me in your paper!