Poor Oren. You can't be a prof in Britain nowadays without being anti-Israel - it isn't really allowed.
" Israel has persistently denied them their internationally recognized legal right to return." link
Such careful language implies the professor is perfectly aware that while the right may be "recognized" that is a matter of politics, not fact. By the terms of the Treaty of Sevres and its successor the Mandate of Palestine, "close settlement" of Palestine by Jews was to be encouraged but nevertheless both Jews and Arabs were supposed to respect the civil and property rights of minorities in the lands that came under their political domination, as they were under the Ottomans. This obligation the Israelis kept - Israel is over 20% Arab - but the Arabs did not fulfill it either in their own lands or in Palestine - the Jews were tossed or made to flee, save for a few in Tunisia and Morocco, and entire Arab villages in Palestine participated in attacking Jewish settlements, or fled expecting Arab armies to win the victory for them.
When these Arabs in the Mandate committed or supported collective violence against Jews they forfeited their civil and property rights under the laws and practice of the Ottomans. Neither they nor their descendants have any legal rights to return. If it wasn't for the politics of the vastly larger number of Arabs focusing their anger on the peace-seeking Jews of Israel and the frightened fashionistas of the West seeking to accommodate them the legal case would have dominated the discussion long ago.