Mallaby’s reference to “John ‘Benedict Arnold’ Kerry” in a column about Wal-Mart’s economic impact was meant, I suspect, to refer to Kerry’s campaign against “Benedict Arnold companies” that reconstituted themselves as Bahamian rather than American entities in order to duck paying their share of the taxes that support (among other things) our army. Mallaby’s point was that if an adviser to Kerry thinks Wal-Mart is OK, Wal-Mart must really be OK, because Kerry was against greedy unpatriotic companies. (As if corporate tax-dodging by locating off-shore and importing tons of stuff from low-wage countries are even remotely related issues.)
No, don’t try to make sense of that; it doesn’t actually parse. But I think that was Mallaby’s (rather dull) point. He didn’t mean to say that Kerry himself was a Benedict Arnold. There’s enough real McCarthyism on the Right these days that we should avoid seeing it where it isn’t.