Setting aside the irrationality of voting, Jason Brennan argues that there’s a better reason that the average American shouldn’t vote: they don’t know very much about the political process.
It’s an interesting read, and while I don’t necessarily agree with it, I think Brennan highlights the importance of political information in a democracy.
There’s nothing morally wrong with being ignorant about politics, or with forming your political beliefs though an irrational thought processes—so long as you don’t vote. As soon as you step in the voting booth, you acquire a duty to know what you’re doing. It’s fine to be ignorant, misinformed, or irrational about politics, so long as you don’t impose your political preferences upon others using the coercive power of government.