An important point to make here is that Israel had dismantled all of its settlements (a total of 21 villages, including the infamous Elei Sinai) in Gaza (during the Israeli disengagement from Gaza in 2005). If the rocket attacks are continuing despite this, then the Israelis are having a valid excuse to claim that the Hamas is opposed to the very existence of Israel.
You may reach that conclusion if you ignore that the occupation as a whole never ended, and neither did Israeli human rights abuses, or interference in the region - the Fatah-Hamas conflict, for example, was largely pushed by the US and Israel (among others). Further, the disengagement served a few other Israeli goals that you omitted there: it increased the separation between Gaza and the West Bank (not only physically in contravention of previous agreements, but also politically as stated above), and allowed Israel to focus on advancing its settlements of the West Bank (which sharply increased at that time).
Your argument is basically that since Israel did something that some may thing was wrong, that it is okay to attack them forever. This obviously makes zero sense. If someone is doing wrong and then correct that wrong there is no reason to attack them once the issue has been addressed.