Israel has always pointed out, on an across-the-board and all-inclusive political spectrum of left to right that any return would affect the Jewish character of the state and the refugees would pose not only an immediate security problem but also a long-term demographuic one.
One aspect, however, is overlooked.
It can be found in this UN document,
UNITED NATIONS CONCILIATION COMMISSION FOR PALESTINE,
COMMITTEE ON JERUSALEM, THIRD PROGRESS REPORT
31. It has already been indicated (see paragraph 17 above) that, for their part, the Arab delegations made a proposal that the refugees coming from certain areas defined on the map annexed to the Protocol of 12 May, comprising those from Western Galilee, from the town of Jaffa, from the central area including Lydda, Ramle and Beersheba, from the southern coastal zone and from the Jerusalem area as defined on the above-mentioned map, should be enabled to return to their homes forthwith. In the course of discussion with the Commission, the Arab delegations have indicated that this proposal bears a territorial aspect, since it envisages the return of refugees to areas designated as Arab territory, and which are in principle to be recognized as Arab territory.
In other words, the return of Arabs could result in Israel's territory being removed from the state's sovereignty. That was the operative intention.
The Arabs, including the Palestinian Authority, have always been nebulous about numbers and the framework of that 'right of return'. They have been also quite clear in the past as to designs on pushing Israel back into the 1947 boundaries, those the Arabs rejected and then went to war on November 30, 1947.
The 'return' of refugees was not a humanitarian measure but a method for undoing Israel's existence then and could be so exploited in the future.