The name change does not have to bother everyone, but it does matter to many of us who have followed the M3 for many years. If we wanted to brag, we'd be driving something with a Porsche crest or a used Aston Martin. Additionally, having a higher number like 4 would be something braggarts would like, so another reason such posts are nonsensical.
Very few people in the general public know what an M3 is, but for BMW to randomly change the name and charge us more for it is displeasing. Now, unless they totally mess it up (which I'm sure they won't) it won't stop me buying the car but I may possibly "downgrade" the badge back to a 3 or lose it all together. If that annoys some people well, all the better.