As has been pointed out, it's freakin' grey belt training! We're not talking about putting people through the MAIT program where Col. Shusko personally beats the living shit out of you (That guy is freakin' hard, BTW). Sure, there's the risk of people getting concussions and injuring ACLs, but that's just a reality of any physical training. The question of pilots NEEDING a grey belt comes probably to two things that I can think of. First is the warrior mindset. It may be a punchline for some people around here, but good groundfighting is a way to breed the seriously aggressive mindset that every Marine should have. Second, and I'm getting this directly out of Col. Shusko's mouth, your belt level is now going to be a distractor item on your Fitrep. So if you're a Captain and you still have just a tan belt, all things being equal, you're kinda behind the rest of the Marine Corps as far as the board can see.
I personally do not look forward to any MCMAP training, but I plan to be a grey belt(whipped on by The MACE, so I know it wasn't a gentlemens course) before I leave The BS.