I have nothing particularly against carrying an empty holster as some sort of symbolic gesture, but I'd much rather encourage everyone to carry a FULL holster. Well, not everyone, but people who know what they're doing.
If you want to make a statement and you're somewhere where it is legal (which is most places) to have a gun-- why not have a gun? Everyone these days walks around with Batman's belt full of gadgets, An empty holster may not draw much attention in a society that is in condition white most of the time. If your goal is to make a statement, make it! An empty holster is making the statement "I could be carrying a gun, but I'm afraid to do it." It might also make the statement "the gun's in the car" to the crooks. Finally, in the unlikely event that something happens that makes you wish you had
your gun, you don't want to stand there looking to the bad guys like the guy who ought
to or might
have a gun.
One does not carry a gun in public because one's hobby is target shooting. Know what you are doing.
Get a well-made secure holster and a good belt. Get a good flashlight. Practice using them often. Get training in gun retention, practice it. Be honest with yourself about your abilities. Do not delude yourself into thinking that you are a combat shooter because you can shoot one-inch groups on a 25-yard target range at your leisure. Outside of the military, most gunfights occur at distances under 20 feet, most much closer than that. Shoot on the move, shoot moving targets, shoot in the rain, cold, and dark. Shoot from the ground, from behind cover, one-handed, weak handed. Run or do calisthenics until you're breathing hard, then shoot. Practice reloads, and even more importantly malfunction drills.
Be courteous. Be alert.