That's not a very accurate quote.
“It’s not surprising then that they get bitter, they cling to guns or religion or antipathy to people who aren’t like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations.”
Why insert the word economic? People are frustrated on many levels. They could cling to guns out of sexual frustration for all I know. I don't see the Marx in Obama's statement. Then again, I'm not William Kristol.
This also suggest peoples anti-trade sentiments are based on something other than a logical and well reasoned response to trade policies that people disagree with. Did Marx claim anti free-trade feelings were merely another opiate of the masses as well? So opposing free-trade agreements is like being a gun-nut, xenophobe, or religious fundamentalist in Obama's eyes. That's good to know.
John Thornton