This. I've never understood why people advertise the fact that they are armed on their vehicles. License plate, decal, window sticker, whatever. Think about it for a minute. If someone was to assault you while you were in your vehicle, would you not rather that they not know you are armed until it's too late to give them any advantage? Why tell them what they are getting in to? The deterrent effect is negligible, at best. IMO, best to not advertise, invite, or forewarn. Break the OODA loop with your response. Harkens back to the basic mantra of dynamic force: Speed, Surprise, Violence of Action.
I am armed 24/7. House, truck, work, garage, shower, wherever. I don't have a blue line decal, 2A, Molon Aabe, or any of that stuff on my vehicles, or house. I see no need to invite a burglary, or warn any potential attacker of what they are getting in to. I don't go looking for trouble. But if it finds me on its' own, I want it to be overconfident when it does.
If it's a matter of life or death, I'll take every advantage I can get.