Maybe.
But there is another way to look at it. If I managed to get appointed CIA director by 0bama, I’d definitely take the job and do my best to use that position to protect the country. At the same time, I’d keep an eye on 0bama. (Keep your friends close and your enemies closer.) The only way I’d resign is if I thought that would benefit my country more than staying on the job.
Not saying Petraeus thinks the way I do, but I wouldn’t rule that out.
There's no way in heck that I'd be party to being an apparatchik to the regime.