If the point is to protect his own life should his job put him in the position where he's facing an armed attacker, killing or not killing the bad guy is irrelevant. Stopping him is. A gun is much much more likely to stop an armed assailant than pepper spray (whether you kill them or not).
If the point is to use a weapon (gun or "less-than-lethal" option) to detain a shoplifting suspect ... well he should stop thinking about that at all unless he intends to become a sworn Law Enforcement officer first and not a humble "Loss Prevention Specialist".
He seemed to be asking about less-than-lethal options because he figured company policy and/or the law would go easier on him in the event he needed to defend his life, not for pacifistic reasons ... so I'd submit that the point missing isn't being done by me here.
More people die every year from fists than from rifles. Punch someone in the head and you might very well have crossed the "deadly force" threshold.