At the meeting of the American Economic Association in Boston last weekend, there were protests organized by a group calling itself “Kick It Over,” who, as the Washington Post styled it, were “battling for the soul of economics.” Their protest included heckling and disruptions of the talks given by Gregory Mankiw, Larry Summers, and Carmen Reinhart.
For his part, Mankiw wrote a short post on his blog after the conference recounting some of the protesting and responding to the charges of the protesters. He reports that one of them asked him how much the Koch brothers had paid him:
After the first session was over, one of the hecklers came up to me and asked, “How much money have the Koch brothers paid you?” My answer, of course, was “not a penny.”
Mankiw argues in his post that if he is making mistakes, it is in good faith: “If I am wrong, it is sincere wrong-headedness, not the result of being on some plutocrat’s payroll, as some on the left want to believe.”
That is an important point to make. Assuming bad faith on the part of a person holding a position different from one’s own poisons, rather than furthers, the conversation. It is also, as Mankiw notes, not an effective strategy to get people to change their minds. Insulting people rarely is.
But there is an even more important point to make: Even if it is true that a person received funding from a donor or foundation with a specific point of view, nevertheless his or her arguments, claims, and positions should be evaluated on their merits. One’s motives—whatever they are, good or bad—are irrelevant to the truth of one’s positions and to the soundness of one’s arguments.
This is an elementary point in logic. Attacking the motives of a person is an example of the ad hominem fallacy, or more generally the genetic fallacy—both of which are, in fact, fallacies.
Now, it is true that there might be cases in which attacking a person’s credibility might be effective, and possibly even relevant. The testimony of a witness in a trial who stands to gain depending on the outcome of the trial might for that reason warrant less credibility. But merely pointing out that the source of one’s arguments might be questionable does not suffice to refute those arguments. The arguments might still be sound, after all.
Thus Mankiw concedes too much when he denies having received funding from the Koch brothers. What he should have responded to that protester instead is: “What difference does it make? If I’m wrong, demonstrate my mistake.”
Too often today speculation about people’s motives passes for acceptable rational discourse. But it is not acceptable. Whether you received funding from Charles Koch or George Soros or anyone else, we owe you the respect of assuming that you are a rational and autonomous person presenting a position in good faith. Our job, then, is to evaluate your position, charitably yet critically, on the merits.
Assuming that one’s intellectual opponents must be some combination of naive, ignorant, or evil is easier than attempting to refute their position. But it is not only disrespectful, it is also pointless. You do not know what your opponent’s motives are. One might be the most evil person in the world, but one’s claims might still be true.
PILEUS 
It takes force to maintain civilization, amongst which is the right to speak without being shouted down. Why were the disrupters not attacked and silenced? Would doing so itself be a violation of freedom of speech?
I get what you’re saying, but in this day and age of professional politicians who say whatever their biggest financial backer wants them to say regardless of their own opinion–if they even have one–there is an assumption that every “expert” has some financial incentive to speak to a particular political bias. You yourself say, “The testimony of a witness in a trial who stands to gain depending on the outcome of the trial might for that reason warrant less credibility.” Trials rarely affect people who do not have any relationship[ to the trial participants, but we are all affected by which way the political winds are blowing. So how is being an invited speaker at an event an excuse to ignore credibility?
You make a good point, wendygoerl. I suppose in some sense we all have agendas, so to some extent no one’s credibility is immaculate. But I think there is a difference between advocating for a position, as for example politicians do, and arguing for a position, as academics are supposed to do. (In my profession, it’s the difference between education and indoctrination.) When someone is offering reasons, argument, and evidence for a conclusion, I think that is importantly different from merely trying anything to get you to agree—especially when your agreement benefits the speaker in some way. The former warrants charitable but critical evaluation on the merits; the latter does as well, though in cases like this the speaker’s credibility might be a relevant factor. My argument pertains to people making good-faith arguments, which falls into the former camp, and therefore, I argue, warrants refraining from speculation about motives.