There is a lot of ad hominem argumentation around, and often the arguments attempt to disprove someone’s beliefs or statements based upon the supposed financial gain they will derive from the outcome for which they argue. There is some truth in this line of attack, Dalrymple says at the Library of Law and Liberty, but it’s more complex than all that:

If someone does something of which we disapprove, something dishonest, and we discover that he has benefited financially from it, we say aha, now we understand!

Often, of course, we are not wrong; yet sometimes the situation is psychologically more complex than what is captured in that cynical “aha” moment. People can easily persuade themselves that what is in their own interest is also in the interest of humanity, their country, the town in which they live. Even the most unimaginative people can be highly inventive when it comes to rationalization. There is scarcely anyone so dull of intellect that he cannot make a thousand excuses for himself when the occasion requires.

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It is a crude view of human life and psychology, however, to suppose that only financial inducement can constitute a vested interest. A worldview, one could say, is as much a vested interest as a block of shares….Worldviews determine economic interests as much as economic interests determine worldviews.