It was a question and answer period. If soldiers cannot ask the questions that matter, then why have a "question and answer" period?
Are you suggesting the entire event was a photo op for Rumsfeld and the soldier did not follow the script?
If that is the case, the only honest course of action is to end the question and answer photo ops.
Military "question and answer" sessions are not, and for the sake of discipline, cannot be as open as you might think. When you wear a uniform, whether voluntary or not, you bear a responsibility of realizing you may not know all the facts.
The military has a chain of command, with those who don't have a "need to know" kept out of the loop. This is to instill trust in one's superiors and in wartime a necessity in event of your capture.
The other reason military services use Public Relations people to answer the press is to protect the naive from revealing information in a public forum to unscrupulous reporters. Its easy to forget by wearing the uniform that you are representing the actual service you are working for and not just being seen as giving a personal opinion. This PRESS abuse aggravates the authority and leadership on whom many of these men's lives depend.
As for your comment that maybe these Q & A sessions shouldnt occur, I would agree only in the sense that the Secretary shouldnt allow unscreened questions when members of the Press are present.