You can get the whole story on the hate mail and the response from Ma Deuce Gunner, but here's the relevant part of MDG's response:

In it you ask: "So what is the point of excessive discipline and exercise?"

Discipline:

IED's.  It takes discipline to be able to keep your eyes on the road for LONG periods of time, to look for signs of threats.  It takes discipline to not randomly shoot back when engaged from a concealed position.  It takes discipline to stay alert, awake, and aware when sitting in an OP looking for bad guys.  It takes discipline to be able to maintain situational awareness in a 360 degree battlefield.  Fighting the kind of war we are fighting requires that we be disciplined and ensure we are ready to destroy the enemy, wherever he is, however he chooses to engage us, in a sometimes VERY monotonous setting.

Also, refusal to follow orders in the heat of battle, due to being undisciplined can and will cost lives.  A disciplined soldier does as he is told, as quick responses and actions can change the tide of battle.  A disciplined soldier keeps his weapon clean and functional.  It will save his life by not jamming in a firefight.  A disciplined soldier maintains proficiency in his art, in order to keep himself and his fellow soldiers alive.  A disciplined soldier scans his sector at a short halt, and doesn't close his eyes because they are not moving, or gets out of the truck to have a cigarette.  A disciplined soldier keeps his helmet on, even when the sweat is running into his eyes, because you never know which window has an enemy sniper behind the glass.  A disciplined soldier maintains his vehicle, and does maintainance out in the sun and the heat or in the cold and the snow, because a broked down vehicle is a good target.

Exercise:

Have you ever worn body armor??

Do you know :

1.  How much it weighs? (24LBS)
2.  Range of motion you have while wearing body armor?? (highly reduced)
3.  How much it increases your body temperature??  (7-10F)

Our body armor alone weighs 16 LBS.  That is the basic set.  Add on the groin protector, neck and throat pieces, flank pieces and shoulder attachments, you are looking at over 24 lbs.  Strap 24 LBS to your chest and shoulders and go run around for a while.  Let me know if the average American physical conditioning cuts the mustard.

Ammo and gear.  Now it starts getting ridiculous.  The standard combat load is 210 rounds of 5.56mm ammunition.  Most guys carry more, I carry 360, and I am a rifleman.  Machine gunners carry 1200, on average.  I also carry handcuffs, a radio, smoke grenades, smoke grenades and illumination rounds for my grenade launcher, pistol ammunition, shotgun shells, a flashlight, night vision, and water in my camelbak.

So, all together, with my armor and all my combat accoutrements, i have close to 70 lbs over my body weight i carry around in the 120F+ heat.  Try going room to room in a hotel in downtown Kirkuk, Iraq, trying to maintain speed, suprise, and violence of action, in the middle of the day with a VBIED going off outside.  Run up and down stairs and hallways, kick in doors, and chase the bad guy through the hotel and alleyway.  Hell, just try and walk 100m down the street on flat ground when it is 133F outside wearing long pants, long sleeves, wearing a 4lb helmet, carrying a 7lb rifle in your hands, a 3lb pistol strapped to your leg, a 5 lb shotgun strapped to your back, and 70lbs on your back and chest, and try to comprehend that A HIGHER LEVEL of physical conditioning is REQUIRED.  I know, I have done it.  I did it last week.

So, why do we maintain discipline and physical fitness??  Because it keeps men alive.  Plain and simple.  Let an army become undisciplined and fat, I will show you an army that will die in place.