The tragedies suffered overwhelmingly by the Palestinians are well documented for those who want to see, just as the obscene imbalance of the moral equation can be witnessed by the whole world if it should exercise its moral judgment.
An analogy that's been used before (though not to this issue specifically) is that of a child who's been pushed into a deep well. It is a universal human wrong, plain for those whose primary concern is human rights, to see such an injustice as an injustice, regardless of one's background. The only other comparison to Israel with respect to its abuses of universal moral principles and laws was apartheid South Africa, opposition to which was near-universal.
In the case of Palestine, what are the sources of injustices seen by mainstream observers (Jewish and Gentile)? The Israeli leadership's intransigence on the issues of: (1) the borders of a Palestinian state; (2) the Israeli settlements; (3) the city of Jerusalem; (4) water (A crucial source of Israel's water is its water aquifers. Most of them, however, are situated within that part of the West Bank annexed by Israel); (5) the question of Palestinian refugees, and (6) the occupation of West bank and Gaza and the obscene use of overwhelming force therein.