I'd be curious what exactly
ABD said in that letter because I"m guessing they didn't literally tell you to "suck it up". We have a first hand experience with an issue and going to ABD HQ upon return. In Spain, at the resort in Marbella, our room was SO smokey it burned our eyes. We are really sensitive to cigarette smoke, and our guides Michael and Natalia did everything they could to fix the situation. Unfortunately, there were no other rooms open (they were totally sold out) but Michael & Natalia made sure we had an ionizer in there constantly and it *did* fix the problem for the most part. They also arranged to have any clothes laundered after we left if we needed it at no cost (we ended up not needing that). When we got home, we contacted ABD about using Marbella as a stop on the itenerary, not so much about how the guides handled it, and we felt it was completely addressed and ABD went above and beyond to make sure we knew our issue mattered.
We also had an itenerary cancelled because of low numbers, and we had trouble getting an answer from the Vacationista about rebooking and ABD covering the difference in airfare for the new dates. In the end, it wasn't resolved, but the next day we got a call from one of the ABD heads and he said they had reviewed the phone call, saw that nothing was resolved, and he personally saw to it that our questions were answered and they sent along some surprises as a way to apologize.
I'm not sure if it's our attitude, or our patience in reaching someone who could help, or what, but we have always felt like any major issues (which dietary needs are definitley part of!) have been addressed and met or exceeded our expectation for customer service.
Just another little story that spoke VOLUMES about travel with ABD (other group travel may do this as well, but we've only traveled with ABD so I have nothing to compare it to). In China, one of our trip mates (who was a solo traveler) became extrememly ill. The pollution had made it nearly impossible for her to breathe, and then she picked up another sick bug and she was really sick. Some activities she couldn't keep up and the guides made sure to arrange transportation back to the hotel for her. One morning, she woke up with a giant, swollen neck and so the guides called a doctor to the hotel. Doc said she needed to go to the hospital, so one of the guides went with her. Stayed with her all day in the hospital, got her settled, ABD was working behind the scenes to arrange all of her flights back home since she was not staying on the trip and would fly out once she could leave the hospital. The guides were in contact with her and made sure she had everything she needed and was safe and well cared for. I am always afraid of one of our family getting sick in a foreign country, but seeing how the guides and ABD HQ handled this scary situation spoke volumes to me. <3