You should see the fights my brothers and I had (one is Spec Ops/US Army, the other- a basic grunt, I - Bn Security Team/Co Sniper, former Tanker). Rivalry is part of a healthy spirit and pride you take in ones branch. Without any "ribbing", you lack pride. When you lack pride, your Drill Instructor failed you.
Ribbing between brothers is a heck of a lot different than ribbing a board with 100,000 readers. Many of these members served in on branch or another. In addition, the ribbing comes at a time when unity and mutual respect is necessary.
I realize you meant this in fun. I'm just throwing my 0.02 in....