Jonesyboy, I'm usually just a lurker on here but I thought I'd login and comment. I can understand your frustration. I was given a 'medically unfit' when I tried to join at your age (albeit not with asthma)
They can't afford to take chances - bith in terms of money, and in terms of your and your colleagues safety. Whatever the problem may have been, they can't take a chance that it could cause your operational effectiveness to drop at a crucial time.
It might be a crushing disappointment, but there are plenty more life opportunnities for you - if you have the skills and intelligence to be considering this career path, I'm sure you can suceed in other life areas - I know I did.