Tyler Cowen sums it up: “Economics is most like a science when people do not care about the outcome of the argument.”
In other words, social science is like science when it’s like science—disinterested. But when it’s like politics, then it’s like politics. I note that American economists are generally able to reach a much greater degree of consensus when they offer policy recommendations to foreign countries than when they offer recommendations to the US congress. That’s not because foreign countries have easier problems to solve.