As everybody knows, Hamas is committed to the destruction of Israel. It has words to that effect in its charter, and it reconfirmed its position when it reached the unity agreement with Fatah.
Less well-known is that many in the Palestinian Authority, of which Fatah is the key player, share this ideology, despite many reassurances about commitment to the peace process, etc. Here's a report, prepared by Palestinian Media Watch, that quotes senior officials, textbooks and state-controlled media delegitimizing and demonizing Israel. They offer many arguments to prove that justice will be achieved when Israel ceases to exist.
Saying a country must cease to exist and calling for its destruction is a distinction without much of a difference. Particularly if, as the Palestinian Authority does, you're paying the salaries of terrorists in Israeli jails.
I'm not arguing that everyone in the Palestinian Authority is focused solely on destroying Israel. On the contrary, many have been working successfully to rebuild the West Bank and so prove that they are worthy of statehood. But they will have a tough time prevailing now that Hamas and Fatah are 'united.' Indeed, I fear they are just about to lose all they've worked so hard to achieve.