Though the Palestine issue may be 'an excuse' for OBL and Al-Q, it is a problem which needs to be addressed on other grounds (what's morally right, for example).
Moreover, it's an issue which can be exploited by Al Q because it arouses enormous passion among a huge proportion of Islamic people (and others). They'd have a job finding 'another excuse' that exerted quite such a pull on popular support.
It's also simplistic and offensive to pretend that the Palestinians want to push Israel into the sea. They may have wanted that once, and Hamas and Islamic Jihad may still want that, but many Palestinians now want no more than a viable state for themselves, preferably based on the 1967 borders.
I quite categorically don't support letting anyone push Israel into the sea, but I would support a forced compromise which either a) gave back enough territory to give the Palestinians a viable state or b) resulted in a secular state to which dispossessed Palestinians had a right of return. Since the latter would mean an end to a religious Jewish homeland state, I would quite understand and support Israel's right to reject it.
But I don't support their total intransigence on the return of land.