Many assumptions in those questions:
1) He has to justify his carry. He does not.
2) He feels he needs to. He did not say that, he said he was carrying. One does not "need" in order to excercise a right
3) He fears for his safety. I see no indication of fear. I suspect, rather, that he does NOT fear for his safety. Once again, fear of safety is not a requirement to excercise a right.
4) He lives somewhere where it is necessary to keep a firearm and ammo while working in an office environment. See above, a firearm being "necessary" is not a requirement for carry if you live in an area that is open carry, '"must issue", or no permit required.
I do however sense you projecting your own fears into the questions. I may be wrong, but if not it's ok. Make you a deal -- I have found that most folks who are "afraid" of guns & people who carry are those that have the least exposure. Actually, this is common in almost all fears. If you are near, I'll take you out, show you some basics, let you fire a few rounds from a variety of rifles, pistols, and shotguns. I'm not saying I can or will change your feelings, but at least I'll know that you are basing those on education, exposure, and experience rather than what you've heard or seen. Message me if you want to take me up on that.