I understand what you're getting at, and if I want I could easily give you counters to those "red flags"
For instance, a young man travelling alone may feel invincible, but it might behoove him to adopt local dress and customs. He was carrying a Koran right? But there's zip evidence he was converting to Islam. What makes more sense is that he was "curious" as he was described or was trying to have "non-offending" articles on him in case he was captured. A man carrying an anti-Semitic(though how virulent I don't know) book and Koran and wearing an Islamic-style beard would probably survive longer than a Jew with the little curls and a kipah(yarmulke), yes?
Occupied is...well, let's be honest--it's what everyone uses. At first, maybe it wasn't a fair word, but now it's quite clear that we are an occupying force. The Americans in Japan were called the Occupational Authority, I believe. It is of note that he pointed out Mosul is pretty safe-appearing. He wasn't making things up or saying "the Americans are brutal." Merely, that there weren't many checkpoints or patrols. hardly the mark of a fanatic leftist.
I could go on, but....well, it just seems that people will take one "fact" and draw the conclusion they prefer. There's simply little reason to believe Berg was anything other than what has been portrayed UNTIL we hear at least an acquaintance describe something else in his character or beliefs.
.......little reason..... huh....you are a most Un-curious person.