Just because you're intelligent doesn't mean you're not irrational. Having intelligence is pretty meaningless except in IQ tests and similar puzzles. Applying your intelligence effectively is what it's all about.

Having intelligence is quite important. Otherwise you have a higher propensity to react with emotions and do irrational things.

See : Modern society

I'm not so sure high intelligence really protects you from reacting with emotions or act irrationally. Plenty of intelligent people can still react very emotionally or even irrationally. Though I suppose reacting intellectually has a higher pay-off for them than for most.

Having intelligence in most cases just means you're better at post-hoc justification of your emotionally-driven decisions.

Agreed, however those who arent intelligent repeat the same emotional responses over and over. Intelligence gives you the possibility of changing that, unintelligent dont have that possibility.

This makes sense. You can make terrible personal decisions (ie, starting a meth habit, fighting a bear) at any intelligence level.

But to make poor decisions on a scale that affects many others, you generally need the intelligence to rise to some level of power.

(There are of course exceptions, like starting a brushfire, etc)