I'm not too worried about thieves, though I do carry multi-thousand dollar cameras through the third world. The more beat-up it looks, the better it fits in.
All I know is, based on my own experience the last thirty years, I got tired of being distracted by people seeing my, first, Canon, and later, Nikon logos, and engaging me in conversation about my opinions of camera equipment. When I started putting tape over the Nikon logo, the questions all but stopped and people paid much less attenton to the camera, allowing me to pay more attention to the photography. I can remember an American soldier eyeing my taped up F and asking, "What kind of camera is that?" Then seeing it had no logo, answered his own question, "Oh, it's just a generic camera."
Obviously cameras don't make us invisible. But to most people, black rangefinders look something like a point and shoot minus all the light-up focus aids. If it's got some tape on it, it just looks less new and less flashy.
Then there's my beloved first Nikomat FTn which needs duct tape to hold the film back closed securely. Love that camera, too, even though I haven't run film through it in a long time.