Thank you Josey Wales (the OP) for bringing this to everyone's attention.
Myself, my family, and friends have suffered just as you have.
First, I have to share two quick stories and then I'll tell you what worked for us.
A number of years ago my buddy and I were hunting elk and eating just one MH meal every night. On the fourth morning it happened. And happened again. And then it wouldn't stop happening. It's hard to hunt elk when you think you might explode at any minute. Our supply of toilet paper was running out quick. The gas was so bad at night that we slept with our heads sticking out of our tents. Even the rain on our faces was still better than breathing that horrid air that was trapped in the tent.
Just this past summer I took my family on a camping trip. We had stopped at REI and my wife saw the MH scrambled egg breakfasts so we picked some up. She loves scrambled eggs so much that she'll sometimes have them for dinner. We had been eating hard boiled eggs, subs, trail mix, and other heavy foods early in the trip but had to go to MH toward the end. After the MH breakfast (which tasted good) I knew that I'd need to go to the bathroom so my family hiked up the trail ahead of me. After I finished my business I was surprised that one of my daughters had hiked back down to me. She said, "Daddy, Mommy needs the toilet paper and doesn't want you to bring it to her". It seems that the freeze-dried scrambled eggs had attacked my wife's normally solid GI tract like never before.
The problem:
There is something about MH meals that upsets some people's GI tract. Everybody is affected differently. BeanO, Gas X, and Tums can't fix it. We've tried. It isn't the result of bad water. It isn't gulping air. It isn't the high elevation. Maybe it's part of the freeze drying process that MH uses. Dehydrated is different than freeze-dried.
I like the taste of MH meals over most other brands. MH meals pack a lot of calories and their meals pack down tighter than other brands (saving space).
We have found that Chili Mac is the most offensive. We've found that Beef Stroganoff is the least offensive. Spaghetti and Lasagna are in the middle. Which is ironic since I love spicy foods and don't typically eat such bland foods as beef stroganoff. Your results may be different.
THE SOLUTION:
What has worked for me is to slowly get the system used to MH meals before a big trip where I'll be eating a bunch of MH. Two weeks before the trip eat a single MH meal. Then the week before eat a couple of meals. This allows your digestive system to adapt to freeze-dried meals. For the last two years that has solved the problem almost completely.