I'm sure they're as weary of this as the rest of us and are getting tired of answering the same questions over and over again.
That's their job. It's inexcusable for them to have an impatient, condescending, or defensive attitude when answering questions from concerned pet owners. If they can't do that with empathy, understanding, and compassion, then they have no business working in the pet industry. I never understand why people on the other end of the phone line at any company stop being human and cannot seem to relate to the person they are talking to, as it they never have to deal with companies and problems themselves, as a consumer or whatever. What planet did they all come from?
It seems like some of them don't realize the way they handle the questions may very well be the deciding factor for a lot of people as to whether or not to continue to buy their products or not. Even if their products aren't involved, the sensitivity and understanding you mentioned in answering the questions will go a long way.
That's for sure. Even if I loved a certain pet food, I would discontinue use if I was not treated with respect from the company. Like any other consumer problem, there is nothing worse than being treated with this kind of indignation when you have a legitimate, serious concern regarding a product, yet it is quite common. Even worse, in this instance, we are talking about the health and potential death of something that we love dearly, and not just a malfunctioning piece of electronic equipment or something, so there is that much more reason for them to have the right attitude. How sad that they cannot understand. This is a crisis for many of us. A crisis should bring out the best in the human spirit, not the worst.
For those companies who are kind with the people who call and email, I'd like to say thank you!
Yes, thank you very much! And maybe to show our appreciation, we should have a thread dedicated to thanking the companies who have responded with compassion and concern.

And maybe one for those who have not.
Edit: Regarding starting a "Kudos" forum, as stated below, thanks Therese! I'll be posting there in the future.