Whoever wrote that comment has an inaccurate grasp of the demographics of Israel and is using an argument Bin Laden made for justifying killing all those people on 9/11 - he felt everyone physically located in the US should die. It's abhorrent and it's advocating a crime against humanity.
Hamas was last elected about 17 years ago when half the current pupulation of Gaza were aged 1 or not born yet. Whether you support them or not is up to you but going around claiming they represent everyone in Gaza is just playing into the IDF narrative.