There is no such thing as double standards in International Relations. I repeat, there is no such thing as double standards in International Relations.
It is not the job of a sovereign nation, to treat interactions with foreign states like a board game, where one gives equal time to each and every other head of state, trades equally with every other economy and wages war with each and every player. Every nation has a distinct relationship with any one particular state at any one particular time, and all states have a different level of economic usefulness, diplomatic closeness and other relevant factors to a state at any time, and it is the job of a state to to correspond one's foreign policy in accordance with those considerations to maximise the benefits gained for his or her state.
This means that even if there were such a thing as 'double standards' applied to Israel it is still likely to be perfectly consistent with a state's perceived aims. It is not the job of the United States to compile a foreign policy that suits the standards or any other moral guidelines that any idiotic left-wing European or especially the god-awful Russia TV hosts, may desire.
Did we apply the same standards to Nazi Germany as we did to other nations? No of course not, because different responses apply to different circumstances. Are liberals really saying, that they would feel happier morally if Iran did acquire nuclear weapons and blow Israel half to hell, and start an arms race with the rest of the middle-east, knowing that regardless of the real-life consequences, they could rest safe knowing that they had treated a gay-killing, theocratic regime with the same standards as secular, democratic state? I doubt it.
Now ignoring the lunacy of attempting to apply equal treatment to unequal recipients, let's consider why Israel may be considered a different kettle of fish in the region we know as the Middle-East. For some reason it is now the popular role of the left to assume the absolute worst of the West and its representatives and the absolute best of the fascists and racists that oppose the West. For example. You are far, far more likely in popular discourse to hear some cretin claim that George W Bush was behind the attacks of 9/11 than to hear that Iran may actually pose a danger. With some perspective, the Bush administration for all of its faults, despite falling on the 'right' of the domestic American spectrum was in the wider scale of things, a liberal government that believed in free speech, democracy and the rule of law. The Iranian perspective has no concept of the things the modern left is supposed to hold dear, namely the separation of the civic and the religious institutions of statehood, rights for gays and women, free speech, free elections etc. Yet for some reason, even when Mahmoud Ahmadinejad openly denies the first holocaust and expresses a desire to bring about the second, people assume that he can be trusted with nuclear weapons. People assume the best of him. He kill gays? Oh well. He's an anti-Semite? Not a big deal. He wants to wipe out Israel? Israel has nukes, why can't Iran hmm?!
Israel's enemies such as Hamas openly express their desire not to have peace with Israel, but to kill every Israeli and every Jew, even those from outside of Israel. Israel, whatever one may think about it's policies in Gaza, does not want to kill every last Palestinian, which they very easily could have already if they wanted, as they already have the nuclear weapons and military superiority. Iran's proxies such as Hezbollah, even have a mushroom cloud as their flag. If you treat Israel's enemies by the same standard as Israel, there will not be an Israel much longer.
When Hitler expressed a desire to wipe out the Jews, it would have been the height of lunacy to allow the Nazis to have acquired the bomb. When Ahmadinejad very plainly states his desire to wipe Israel off of the map, it would be the height of insanity to let him get the bomb.
I never would have treated Nazi Germany with 'equal' standards and I'm very proud and unashamed to say that I will never play a moral equivalence between Israel and Iran. Never.