These guys are griping. They are allowed to gripe. The mistake here was the Pentagon choosing to make this session public. It's not the soldiers' fault that they asked tough questions after being invited to a session where they were told to ask tough questions.
Bad PR move from the Pentagon.
You are exactly right. If Rumsfield was serious about his "tough question" dialogue, I don't believe they should have allowed any cameras or civilians in the meeting.
Instead, it looks like a creepy PR move gone bad.