Their entire argument consists of negatives... there is no report during Ramases II reign of any plague, natural disaster of unusual size, or loss of his army. This is a circular argument... but absence of evidence is not evidence of absence. If Ramases II is the WRONG PHAROAH, then of course there is no evidence of the Passover. They are looking in the wrong time frame by about 200 or so years.
The Egyptologists' approach is like future historians looking for evidence of Man Landing on the Moon during the American Revolution and discovering that Washington, Jefferson, Adams and Franklin did not mention the moon landing in their letters and documents. Not finding the evidence where they are looking, they "authoratatively' declare the moon landing never happened and congratulate each other on debunking another 'myth'.