The soldier didn't threaten him. He was apparently interviewing the soldier and the soldier gave a candid answer. I don't see a problem.
Besides, some guard posts come with the special intructions to 'use deadly force' to prevent unauthorized entry by anyone.
This certainly sounds like an appropriate order at this site.
This is generally the way SF works. They don't have the time or resources to babysit idiots who insist on getting in the way,and in a circumstance like this a "outsider" could screw-up the collection of vital information,or even reveal the identities of the SF'ers on the ground. If one of these guys is on guard duty and he tells you to not come any closer or you will get shot,my best suggestion to you is to take him at his word. If you don't,you WILL get shot.