I also strongly believe that the cause is the former - centuries of institutionalized persecution, a vicious cycle of poverty, etc. Why not respond with that? I can understand it being frustrating but we can't just shut off discussion of uncomfortable truths.

I have encountered many situations in my own life where liberal-minded people will outright deny claims like that. Unfortunately those are the statistics; denying facts helps no one. There is an explanation for those numbers - that is what the response should be.