The more I think about it, the more disgraceful that column was. Pure identity politics paranoia. A Jewish columnist sees a black man running for president and the first thing he asks himself is: where is this guy on Farrakhan? And Obama has to disprove his connections, even though there is not even a smidgen of evidence connecting the two, and even, as Greg Sargent points out, Obama's own spokesman explicitly disowned any support for Farrakhan in the same column.
If Obama has to disown a man he has never had anything to do with and a man whose toxic racist politics Obama has consistently and continuously opposed with all his might, then every black candidate is forced to jump through Cohen's petty little racist litmus test. They're all guilty of anti-Semitism until proved innocent. And Cohen's transparent disavowals of such an insinuation make it worse not better.
We are learning a lot through this primary process - especially about some powerful white liberals and race. What we're learning isn't pretty.