That is a good point you bring up. However, before we were able to impose democracy on those countries we first had to firebomb the city of Dresden, and you know what became of Hiroshima and Nagasaki. Do we really want to do that to the land along the West Bank and risk bringing WWIII into full swing?
What we had to do was convince the people of Germany and Japan that their leaders' ambitions were hopeless, that they had no choice but to accept our peace terms. That required massive bombing only because Germany and Japan were industrial powers: Until we demonstrated that they could not hope to continue to produce war materiel, they could still cling to belief in eventual victory. The PLO, on the other hand, is not an industrial power. Arafat's aspirations can be crushed without indiscriminately killing his subjects.
The PLO gets its materiel from Iraq, Iran, Syria and Saudi Arabia. To defeat the PLO, we need to cut off that support permanently, which will require a variety of diplomatic, military and covert initiatives, starting with regime change in Iraq. Then we have to convince the Palestinians that the world will never rise up against Israel on their behalf, which will require a constant media campaign condemning terrorism. Finally, we have to eliminate the PLO mafiocracy's ability to suppress dissent and kill moderates ("collaborators").
These are all major challenges, but we won't have to do anything similar to Dresden, Hiroshima and Nagasaki. Quite the contrary, in fact: The scenario most likely to result in nuclear destruction in the Middle East is a "hands off" approach. Sooner or later the Arab nations, unless forcibly dissuaded from their never-ending quest to destroy Israel, will box the IDF into a corner from which nuclear launch is the only option.