There is one condition on which it is entirely legitimate to raise and to pursue questions about interests and motivations. If and only if the original questions of truth and validity have been settled, then—at least from the point of view of soundness of thinking—it is perfectly legitimate and it can often be very illuminating to raise and pursue such questions. For, given that some individual or some set of individuals is mistaken and now known to be mistaken, and given that we have no evidencing reason to believe that individual or set of individuals to be in general intellectually challenged, then we may reasonably expect to discover what it is which is misleading that person or set of people. Yet it will not do—notwithstanding that is all too often done—to offer more or less speculative answers to such consequential questions as a substitute for, rather than as a supplement to, the direct examination of whatever were the prior issues.
(Antony Flew, How to Think Straight: An Introduction to Critical Reasoning, 2d ed. [Amherst, NY: Prometheus Books, 1998], 71)
Note from KBJ: Progressives violate this rule far more often than conservatives, though I don't know why. Suppose there is disagreement (controversy) on some evaluative matter. Instead of showing that the conservative's belief is false, or that the conservative's grounds for the belief are inadequate, the progressive tries to explain why the conservative has the belief. This is bad enough, but the progressive's explanation is almost always (1) speculative and (2) insulting. For example, a conservative believes that abortion is wrong. The progressive says that the conservative believes this because he or she wants to oppress women. A conservative believes that Barack Obama is a bad president. The progressive says that the conservative believes this because he or she is biased against black people. (Leave aside the fact that Obama is only half black.) A conservative believes that homosexual "marriage" is unjust. The progressive says that the conservative believes this because he or she is biased against homosexuals. A conservative believes that God exists. The progressive says that the conservative believes this because he or she wants a divine father. A conservative believes that the global-warming hypothesis is false. The progressive says that the conservative believes this because he or she is in the pocket of the oil companies. Get the idea? Instead of joining issue with the conservative, the progressive evades it. It's sad that so many progressives would rather speculate about the causes of belief than examine the grounds of belief. Certainly no philosopher should have such a preference. Philosophy is about grounds, not causes.
Keith Burgess-Jackson, J.D., Ph.D. 