You will have to ask them. I have enough trouble explaining why I say what I say, never mind taking responsibility for the statements of others, especially such blatantly irresponsible statements like the one you quote. I believe one can reasonably say that there is not sufficient physical evidence to prove that the exodus as described in the book of Exodus happened. Obviously, it is not possible to prove that no sort of exodus of Jews from Egypt ever happened. It is simply not possible to prove that it did NOT happen. Perhaps one can say something like this: an exodus of the size implied by the book of Exodus is of a scale that it is very unlikely such a thing occurred. I would not necessarily agree with this statement, but at least it would be a responsible one, whereas the statement you quote is quite simply irresponsible. It is quite obviously made, not because of the evidence, but because of an agenda.
As for the conquest of Canaan, here is what I think would be a reasonable statement from a scholar who is skeptical of the Bible: We know that the Israelites had conquered a significant portion of Canaan by the 13th century BC because they are specifically mentioned in the Shishak inscription. However, our knowledge of late Bronze Age events in Canaan are far too sketchy to say that we can confirm the events recorded in the Book of Joshua. In fact, there is some evidence which implies that at least some of the details did not happen. Again, I would not agree with this statement, but at least it would be a responsible thing for a scholar to say.
This is a familiar pattern. Perhaps it is because these people have a demon in them. Perhaps it is because they are influenced by Satan. Perhaps they hate Christianity. Perhaps a religious parent beat them. I cannot explain why some blatantly biased scholars make such irresponsible statements. Perhaps you can tell me why you think they say such a thing which obviously cannot be proved by evidence.