The relevant question is, is this fair?
The people who criticize Israel justify this double standard on the basis of Israel's holding itself as a moral beacon for the world. As one commentator put it:
To start complaining that people actually hold you to the higher standards you claim for yourself would be hypocritical at best. It is frequently asserted that Israel is the only true democracy in the Middle East - a beacon of light in a region of darkness. Israel has a free press, and it claims to defend and uphold the rule of law. This should give Israel a moral edge over its enemies, including Hamas, and it does. But this coin has two sides: if you claim to respect higher standards than others, you should accept that others hold you to these higher standards. If the moral high ground is part and parcel of your reputation (some even say, your right to exist), then you should undertake every effort to safeguard it.There is an interesting fallacy implicit in the part of the argument I bolded. Israel certainly claims to respect higher moral standards than her neighbors and enemies (others), but it is being judged by other Western nations (others.) The author conflates these "others" in making his (or her) argument, and once this is apparent the argument falls apart.
Even if all the accusations about Israel's behavior in Gaza are somehow true, it doesn't come close to putting Israel and Hamas on the same moral plane. Israel can still accurately claim to have the moral high ground compared to the Gazan terrorists.
Even without that fallacious use of the word "others," however, the more generalized argument in favor of double standards is that Israel, as a freedom-loving democracy, should be scrutinized against higher standards the same way that one would expect Mother Teresa to behave differently than Saddam Hussein.
There are three problems with this argument.
One is that when a person or a people set for themselves a higher standard, it is up to them to judge and enforce it, not third party observers. It is quite fair for objective third parties to judge Israel against the Geneva Conventions or any other standards that theoretically apply to everyone equally; it is quite unfair to hold Israel to any standards beyond that. One can observe that Israel falls short on occasion from its own self-imposed moral standards but it is quite hypocritical to judge Israel based on that. Only Israel has the right - and indeed the obligation - to judge its own people based on a higher moral code. When others do it, it is not based on morality; rather it is based on jealousy.
When one starts to judge Israel based on arbitrary "standards" beyond what is expected from others, it quickly devolves into an exercise of demonization - especially when these standards are set arbitrarily high, even beyond Israel's own self-imposed standards. Too often, Israel is judged against perfection, while others are merely judged against the status quo or their previous behaviors.
A second problem is that the people who judge Israel tend to base their definition of morality exclusively by how Israel treats the enemy. In the most simplistic terms, they argue that all death is bad and therefore war must minimize the deaths of the enemy. They tend to disregard the higher moral imperative of self-preservation. From their perspective, all human lives have equal value so therefore Israel has no right to value its own people's lives above those of her enemies. They apply this incredibly simplistic formula to Israel's actions and then conclude that Israel must be immoral by valuing her own lives higher. In other words, they impose their own warped sense of morality on others, and the others who have a different or more realistic moral code inevitably fall short.
This "moral" perspective then says "Israel has the right to defend her citizens" but cannot find a valid way, in its universe, for Israel to do just that. These people often do not believe in the validity of nation-states to begin with and they reject the idea that any war can be just. To them, a "moral" nation under siege must turn the other cheek and let its own citizens be terrorized because they find the alternative too distasteful. This is, ultimately, immorality being passed off as super-morality.
To these people, how terrorists act is irrelevant. Sure, they are immoral, but that doesn't give their victims an excuse to stoop to their level. You cannot ever go on the offensive against terror.
Which brings up the third issue - the idea of a "fair fight." According to Israel's critics, when a moral party is in a fight with an immoral party, the moral party must consciously give the immoral party the tactical advantage of not being bound by the accepted rules of war. While Israel's critics wil never hesitate to remind the world of Israel's huge military advantage, they will not look at how much of Israel's military budget is dedicated to expensive devices and methods meant purely to minimize deaths of both the enemy and Israel's citizens. A Qassam rocket is cheap, a fortified playground is expensive. A mortar meant to kill as many Jews as possible is much cheaper than a smart bomb that can be deflected at the last second if a civilian appears.
The problem is not only that Israel is being held to impossibly high standards, but that Israel's enemies are being held to no standards at all. A single civilian death on either side is a victory for Hamas and there is no outcry and little criticism about this self-evident fact.
Israel is not allowed to win, because a victory is considered immoral. Yet the artificial prolonging of the conflict, the coddling of the terrorists and the sympathy for those who want to see a literal genocide agains the Jews of the Middle East is what is, in fact, immoral. The problem is not simply a double standard; it is the application of a fundamentally immoral viewpoint as if it is truly an ideal.
Israel must constantly walk the fine line between the morality of protecting her citizens and the morality of minimizing damage to innocents on the other side. Her critics are not nearly as concerned about one side of that equation. And that is the problem in a nutshell.