The point of the essay is even if the story is not true, it makes no real difference. That's not really a good enough reason to live and die for Jewish continuity, or continue a dangerous and unpleasant dispute with the Arabs, for example. After all, they're lying, but our history is a myth, so why don't we just drop our annoying claim to Schmalastine? This is Haaretz, remember?
from the article: All Jews were once slaves in Egypt, whether history proves it or not