I'm no expert, but I believe that with a Civil Engineering degree, even as a Concientious Objector, you could still join and accelerate your naturalization process, if that is your choice.
However, I have read stories about COs who found themselves with orders to battle zones and, as a Civil Engineer, you would be a prime selectee to help re-build Iraq or Afghanistan.
My advice is if you're not willing or prepared to follow orders and go into battle to defend this country, don't join. A military that is full of COs is not very beneficial in the event of all-out war. Given the current state of the WOT, we are not far from all-out war as it is.
Pick your poison carefully. Once you sign the contract, you belong tothe US government and they don't believe in "king's X".
Believe his reference to CO meant commissioned officer.