Who are we to say that the Germans shouldn't be killing Jews. What they're doing might be what's right for their culture in that time and place. Maybe when you shoot them in the back of the head while they're on their knees in front of a grave they dug for themselves the gunshot wound spouts out golden coins, precious stones, and candy! After all, jew is the first 3 letters in jewel.
Well, America and Britain did
let the Jewish people die. The massive slaughter of Jews, homosexuals, gypsies, and the mentally deficient was not the reason for WW2. Do not kid yourself, or adopt your smug hindsight sense of superiority about this. The reason there was WW2 is because of the invasion of Poland.
This is also why we, the first world intervened to stop the genocide in Rwanda, to stop the exterminations going on Cambodia. And female genital mutilation in Africa. Or political repression in North Korea.
Now, if the first world had had the stones to intervene then and say "Stop, what you are doing is wrong" then they would have the right to tell other countries how to act now. Instead the choice to only intervene in the easy cases makes your argument morally bankrupt.
Further, extermination based on religious-ethnic grounds is not the same thing as outlawing certain practices. It is an utterly invalid comparator - the choice to do so is pathetic. Why? Because I refuse to succumb to any easy 'get-out-of-debate-free' card based on my religion and heritage.
There are two choices. Complain or do something about it. When NATO bombed Serbia, it was the choice to try and do something about it, and this was met with international outcry.