One collection of stones on top of others is a pile of rubble, while another can amount to the Great Wall of China or Cathedral of Chartres. Likewise, some historians obscure history by cynically throwing together historical vignettes and opinions while others reveal it by presenting the fruits of earnest research.
Oliver Kamm picks through the former and finds nothing but the collapsed remains of a facade.
In other words, what happens when you seek the help of Howard Zinn to back up an assertion that the horrible carnage of Hiroshima and Nagasaki were practically without military value in terms of the Pacific War (and not the cold war)? (An even bigger rubble heap is the pointless collection of human misery that Zinn amassed - and was lucky enough to find a mass market for - in The People's History of the United States.)
Kamm is kinder than I would be in stating that "I am certain Zinn is an honest historian, but equally certainly – on the subject on which Media Lens has sought his advice, at least – he is an incompetent and ill read one."