I have been scanning in my home/vehicle for the last 10 years or so and have never had an issue with law enforcement. My last two trucks have had at least 2-3 whips on them and no one to my knowledge has given them a second look. I even asked a local deputy what he thought of people with scanners and he said "scan away!"
Two of my neighbors are LEOs and we routinely have our scanners out while we're working in the garage, hanging out at the fire pit, etc. and no one has expressed any concern with my being "in the loop".
The only time I ever got attention was when a local police officer saw me with my hand up to my mouth in the truck, and turned around to pull me over. He had assumed I was holding a cell phone to my face (which is illegal in WA), but I showed him the mic for my 2M mobile and explained that that's what I was using. A quick look at my amateur license and I was on my way. He never said a single thing about the scanner audio in the background (I thought it would be fun to hear my own traffic stop so I turned it to scan while I was stopped).
I doubt the general public cares about or even notices the antennas. Most people can't be bothered to even notice traffic signs or other road users -- how could they be creeped out by an antenna they most likely won't see?