The explanation for the Jewish connection to Eretz Yisrael is typically based on the accounts of the Bible. Often, this line of argument would end with the Bible, or to paraphrase Ruth Calderon, goes from Tnakh to Palmach. Unfortunately, arguing that the Bible and the Bible by itself justifies Israel's existence plays into the hands of those who purvey the narrative that a bunch of Poles opened the Bible sometime during the 19th century and concluded that what they read gave them the right to travel thousands of miles away and dispossess the native peoples of that land. Further, emphasizing legend, as opposed to history, enables Abbas to counter with his own legends, such as Palestinian descent from the Jebusites. After all, his legends can't be readily disproved if one doesn't look at the record in between the time of those legends and today.
It is the historical record in between the legendary accounts of the Bible the advent of modern Zionism, for which there is no parallel Palestinian claim that can be spun, that distinguishes our claim to the land from that of the Palestinians. It is the redaction of the Mishnah in the early 3rd century and the Palestinian Talmud in the early 5th century that demonstrated the continuing connection of the Jews to Eretz Yisrael after the Bar Kochba revolt. It is the generations of Masoretes and paytanim in Tiberias that demonstrates the post-Talmudic connection of the Jews to Eretz Yisrael. It is the settlements established throughout the centuries and supported by Jews in the diaspora that demonstrates the connection of the Jews to Eretz Yisrael after the Crusades.
All of these are mentioned every now and then. However, they are not mentioned nearly often enough. As a start, whenever the Biblical connection to the land is mentioned, mention some components of the post-biblical connection as well. Whenever Abbas mentions his supposed descent from the Jebusites or Canaanites, mention how we maintained our connection to the land between the 3rd and 15th centuries and ask how his people maintained any sort of connection during that time period.