He came into my office and said we needed a "no gun policy".
In the late 1980's, we had a few workplace shootings that got quite a bit of publicity. Handgun Control Inc. and the Violence Policy Center capitalized on the phenomenon. They contacted the Human Resources departments of countless major companies and informed them that they could be next if they allowed guns in the workplace. That's when we started seeing a cascade of bans.
Throughout the following decade, they went further and distributed literature that warned companies about the dangers of having employees who owned guns at all.
Plain fact is, they were convincing, the effort was pervasive, and it's decades old. The propaganda is so ingrained at this point, most companies assume that not having a "no guns" policy is asking for catastrophe.