The thing is, Kristol is basing this on what is very likely an all-too-common misinterpretation of Marx.
In analysing Marx, Kurt Vonnegut wrote:
...supression of religion was supposedly justified by Karl Marx's statement
that "religion is the opium of the people." Marx said that back in 1844,
when opium and opium derivatives were the only effective painkillers anyone
could take. Marx himself had taken them. He was grateful for the
temporary relief they had given him. He was simply noticing, and surely
not condemning, the fact that religion could also be comforting to those in
economic or social distress. It was a casual truism, not a dictum.
Which basically comes down to Obama portraying himself as less a fan of religion than Karl Marx is generally believed to have been.
And that can't be good.