This is also true in the knife world...especially if you carry something in the large-ish category.
Or, leaving pocketknives out of it...something like the Clinch Pick or Push Dagger...or...sap or other striking implement...even where legal...will elicit a similar response.
LEOs, like anyone else, are part of the larger herd, and react similarly to seeing what they consider outside the norm.
If I'm honest, I'd probably have a similar reaction internally, even if not expressed, during a stop. I don't think it's abnormal or unusual.