Sabbagh recognized the danger of the situation in Lebanon when, in April 1975, twenty-six Palestinians were shot to death by Phalangist forces in ‘Ayn al-Rumanah, in retaliation for the assassination of two of their bodyguards.
Abu Iyad asked Sabbagh to convince the Maronite patriarch, Antonius Butrus Khraysh, to condemn the killing publicly in order to preempt a further deterioration of the situation.
Sabbagh, accompanied by a member of the Phalangist party, visited the patriarch, who agreed to make a statement on the radio that same evening condemning the killings.
Sabbagh strongly believed that had that meeting occurred between the two leaders at the onset of the conflict, it may have prevented much of the bloodshed and disaster that took place in the following days, months, and even years.
In 1982, after the Israeli invasion of Lebanon, Sabbagh accompanied by Munib al-Masri and Abdul Majid Shoman, went to Saudi Arabia to ask King Khalid to intercede with the United States in an effort to stop Israel's bombing of Beirut, to allow the PLO to leave the city.
Most controversially, his 1978 meeting with the Phalange, first agreed to and then denounced by Arafat, provoked condemnation from the Lebanese and Syrian governments as well as from Palestinian opposition groups.
[2] The founding board of trustees members included Sabbagh himself, his three children, Khalil Abou Hamad, Adel Afifi, Samih Alami, Walid Khalidi and Abdul Majid Shoman.
[2] Through the Diana Tamari Sabbagh Foundation, one of the largest Arab charitable foundations, Sabbagh supported institutions of higher education across the Arab world and the West, and has influenced a range of dialogue initiatives, notably in the United States at the Council on Foreign Relations, the Carter Center, and the Center for Muslim - Christian Encounter, and in Palestine within the Palestinian Initiative for the Promotion of Global Dialogue and Democracy (MIFTAH), under Hanan Ashrawi.