Benjamin Friedman has a good take U.S. foreign policy analysis and the factors that shape it:
'Analysts tend to reflect the views of one party because they hope to serve it or because their employer does. Those pining for jobs in the Obama or Thune administration are not going to tell you exactly what they think about Afghanistan without considering how their would-be bosses would react.A fourth bias in defense analysis is what academics call a selection bias. Just as people that go into the international development business are likely to support increased foreign aid, defense analysts are more likely than most to be hawkish people.
Fifth is social convention. When these pressures point in a particular direction, it seems impolite and for many people uncomfortable to swim against the tide. And we unconsciously adjust our political views to fit in with those around us.
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As Friedman writes, you really can't change this incentive structure but it would benefit everyone to be more open and honest about it.