Well, not only that but going armed to the terror of the public would require you to:
1. Arm yourself with an unusual and dangerous weapon,
2. For the explicit purpose of terrifying others and
3. Go about on public highways
4. In a manner intending to cause terror to others
Open Carry is NOT going armed to the terror of the public. While they may have some other ordinance about OC, they still couldn't technically charge you with that. Of course they just told you they'll surely try though. It's nice to know that they threatened to charge you with a crime you did not even mention committing.