> The opposite -- a presumption that people always vote in their own best interests -- is equally condescending because it's an expression that nobody can really believe.

It's hard to believe that every position of a candidate you vote for is in your interests because that's basically never the case.

Suppose I support the elimination of most federal programs and taxation (let the states do it) but I think that a federal carbon tax which is paid out as a dividend to the citizens is a great idea, because it's a national/global issue and pricing externalities is the legitimate purview of government. Who shall I vote for? I have never seen a single candidate proposing to do both of those things.

In a sense the only way for me not to vote against my interests is to stay home. At the same time, there are two candidates on the ballot that are very much not the same as one another. So it's not so much a matter of "voting against your own interests" as choosing which of your interests outweigh the others.

But assuming that anybody who makes a different choice than you is a fool is very condescending.