Personal taste notwithstanding, I have never been able to see the point in trying to identify ones vehicle as something that is not. How is putting Cobra emblems on a non-Cobra Mustang unlike an import tuner boy putting Type R emblems on his non-Type R vehicle? Some argue that if they have Cobra-spec parts this becomes "OK" but the emblems exist to identify what a car is. A snake on a fender of a Mustang means that it is a special model, and if your car is not a Cobra, it should not wear Cobra emblems. In a nutshell, the emblem conveys the cars identity, and identity theft is a crime.
That is just my perspective on it, and I think there are many ways to personalize your car without tacking all sorts of "Mustang-related-but-not-really-applicable-to-this-specific-car" emblems on it.
HOWEVER there are some loopholes...and they are exploited when a situation is truly unique. A hypothetical example of this would be a 4-eyed Mustang that packs an 03 Cobra drivetrain and suspension. The Cobra emblem in that case would be a subtle tip that there is something different underneath the skin of this pony.
That being said, simply slapping inaccurate badges on a car because they "look better" doesn't quite jive in my book.