When  it comes to vilifying Israel, hyperbole and total fraud are the rule. This is true of one the main things said about the Gaza Strip in order to cast Israel in a bad light. But Gaza’s population density is not Israel’s fault. And anyway, Gaza is far from the most densely populated place on earth. But if there are those who truly believe, or really, really need psychologically to believe that that claim is true, then there is  a solution. Allow Gazans to emigrate from Gaza. There are several Arab countries with much available undeveloped land. There are also quite a few non-Arab lands that could absorb Gaza Arab immigration.

Here are population and area stats comparing the Gaza Strip with Manhattan Island. You can calculate the density by dividing total population by area (in square miles or square kilometers).
Manhattan  Island

population  (2012)
1.69 million
22.7 square miles (or 58.8 square kilometers)
Gaza Strip
1.76 million (Index Mundi – 2013)
1.8 million (CIA World Factbook — 2014)
360 square miles  (Information Please)
density of Gaza Strip
9,713  per square mile (Information Please)
density of Manhattan Island
74,449 per square mile
This web page has numbers for population density in many countries (here)
So we see that Manhattan Island is considerably greater in population density than the Gaza Strip. It is 7.66 times denser. That won’t make much difference to the fanatic Israel haters, but that is the real figure.
Nevertheless, those who think that Gaza is too densely populated should allow Gazans to emigrate to greener pastures.