There’s this phenomenon studied by public choice theory called “rational ignorance.” That’s when people do not seek out information in a civic-minded way: we are tempted to think them irrational, but if the costs of obtaining the information outweigh any possible benefit to them individually, then becoming informed is irrational. When an aggregate of rationally ignorant voters vote, this can be a problem. Further light is shed on that phenomenon when we ask “what are true beliefs for, why have them at all?” Presumably a big part of the value of true beliefs is that they help me make rewarding decisions, which is why I want to know what time the bus is coming, but not the next time there’s going to be an election in Belgium. OK, but not all irrationality is about beliefs; the Stoics especially were aware of this. Part of practical reason is being able to control your emotions. Why? Because morality aside, yielding to passion can cause decisions that incur costs to the decision-maker (breaking a prized possession in anger, and then regretting not having the prized possession). This suggests an analogy: there is such a thing that we might call rational intemperance. There are costs and benefits to being intemperate – feeling good temporarily, but breaking things you’ll want later. But what about being verbally intemperate towards total strangers on the other side of the country, or the world? Need we ever worry about “breaking” our cherished relationships with them? And the political interest of this should be obvious: just as rationally ignorant voters in a democracy can cause harmful policies, rationally intemperate voters can cause: excessively punitive laws, partisan gridlock, wars, etc. etc.
But especially wars.