Why don’t you simply put this stipulation into the argument:
Who is killing more TODAY?
Or,
IN THE LAST 100 YEARS who has killed more?
Isn’t that what this is all about? What are we going to do about the problem in MODERN TIMES? No need to dust off the history books to solve this riddle.
Have them check out “thereligionofpeace.com” website. They keep a running tally of atrocities committed by ROP enthusiasts compared with those perpetrated by other religions. There is another website, “religionofpeace.com” that is a Muslim site that paints a picture of Islam as a benign,near-paradise on earth. Quite a contrast between the two.