Crossfire is apparently the place of the "JFK Death list" with "103 Mysterious Deaths" of people who thinks Marrs might have known too much or something like that. McAdams covers it here
http://mcadams.posc.mu.edu/deaths.htm
Some of the supposed sinister deaths are just bizarrre. For example there is:
Jimmy Levens, who was Fort Worth nightclub owner who hired Ruby employees. Ooooh, he was in on it. How'd he die? Natural causes. Whoops. But jeez, even if it were murder or something, if that is the extent to which you are going to expand the field, then of course you are going to find some things showing up. And even then, Marrs failed miserably.
Then there is this guy: Garland Slack, a man who said Oswald fired at his target at rifle range. So apparently, he saw Oswald once. They had to shut him up! So they killed him! In 1978, 15 years after the assisination.
That's another great thing about Marrs's list. The number of "mysterious deaths" that occured
Ask your friend what he thinks is good evidence in Marrs's book? Here is a comment from the McAdams site: "Unfortunately, this kind of logic is rampant in the research community; I've often heard colleagues of mine say things like, "What are the odds that all of the evidence of conspiracy is wrong?" Nothing better illustrates this than Jim Marrs' Crossfire, which simply collates, in terms of conspiracy evidence, everything but the kitchen sink, without really discriminating between good and bad evidence. Crossfire makes its case through sheer volume: no one piece of evidence in the book is especially compelling (let alone proof of anything), but there's 590 pages of it--two and a half pounds of conspiracy, thank you very much."