I agree with you on the point of taking pride in your v6 or whatever, but I think you can do the upgrade appearance... as long as you don't go too far.
Adding a cobra emblem to the fender, I believe, is acceptable because I think it's just a sweet-looking badge. It's not that I'm trying to pass my car off as a shelby.
Now... adding the SHELBY letters to your trunk, conversely, I think is going too far. because then you're actually crossing the line and trying to pose your car as a shelby.
Long story short, I think you can upgrade the appearance of your mustang as long as you don't cross that "poser" line.