Your history was only partially right. It's true about the Palestinians having chased the Christians out of the Damour but it was about 3 years later that Sabra-Shatilla occurred during the occupation and with the help of the Israelis. It was supposedly done to avenge the assassination of the Christian leader and Israeli ally, Bachir Gemayel, with whom the Israelis had stopped waltzing. Some say Bachir was killed by the Syrians but the majority believe it was by the Israelis to finish off the camp Palestinians after the others had been put on boats to Tunis. You are right though about Lebanon not having a rosy picture either. Everyone being guilty does not justify anything.
Key U.S. House Democrat cites troublesome issues in Iran nuclear deal (Reuters)