Well you make an interesting point. I have heard that some of the neocons are particularly intelligent people, at a level of genius IQ. I think the same is reported of someone like Henry Kissenger.
It is true that politics will more than likely attract powermongers. Many of these power mongers are also extremely intelligent by typical standards--i would guess top 10 percent.
But we could look into that more.
The fact is, I don't see these intelligent people making more ethical decisions or even better policy decisions, etc. than your average joe in the top 50% of intelligence would make.
There is a base level of intelligence one would need simply in order to understand certain political/ethical situations. After that, I would argue that psychological stability and emotional maturity would more than make up for any gaps in intelligence.
Unfortunately, it is difficult if not impossible to test for these important qualities and intelligence will more often than not be overvalued.

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