Benen was writing about Democratic strategist Mara Vanderslice, and her consulting firm, Common Good Strategies, which advises Dem candidates on broadening their appeal to conservative religious voters. Benen writes:
All of Vanderslice's advice — speak at conservative religious schools, buy commercials on Christian radio, and organize meetings with politically-influential clergy — sounded largely inoffensive to my secular ears, right up until Vanderslice addressed church-state separation.
(Benen quotes from a NY Times article:) In an interview, [Vanderslice] said she told candidates not to use the phrase "separation of church and state," which does not appear in the Constitution's clauses forbidding the establishment or protecting the exercise of religion.
"That language says to people that you don't want there to be a role for religion in our public life," Ms. Vanderslice said ...
That's spectacularly wrong, and frankly, a little dangerous. The separation of church and state is what guarantees religious liberty in the United States.
It's the principal reason religion has flourished in this country — because believers have always known that they are free to worship (or not) without aid or interference from the state, which is bound by the Constitution to remain neutral on matters of faith. No matter what your beliefs, the separation of church and state protects you, not inhibits you.
To tell candidates to avoid support for church-state separation, and to insist that the constitutional principle is somehow hostile towards religion, is not only to play the religious right's game, it's endorsing the movement's rules.