I became a special education teacher because I grew up with a sister who has a significant developmental disability. Now that we are both adults, I am her conservator, because our father is deceased and our mother is in poor health. So I can relate to both sides of this equation.
As a family member, I know how important it is to know that my loved one is getting the concern and attention she needs and deserves. I do get annoyed when the adult program she is now in doesn't communicate with me, especially when it is an issue that could have more easily been resolved had they been in touch with me as soon as the problem arose.
As a teacher, I make a sincere effort to communicate with the families of my students. In addition to the classroom phone number, I give everyone my email address and my voice mail number, and I send a communication notebook home with each child. Ideally, I would be able to jot a quick note daily, but in reality, I have 10 students, and if I spend even 3 minutes writing to each person, that's 30 minutes a day. I don't have a planning period like the general ed teachers do, and because of the special needs of my students, I cannot just send them out to recess or to the cafeteria; I need to be present with them. So I am literally on duty from the moment the kids arrive until they leave in the afternoon. I only use the restroom after checking that my assistant is OK with managing things for 4 or 5 minutes. Our kids need assistance with toileting, and about half are not toilet trained or have accidents. About half my students do not communicate verbally, and nearly as many have significant behavioral issues, including physical aggression. And then there is the need to work on the specific IEP goals of each student; with 10 students, we are responsible for implementing activities and collecting data on anywhere from 60 to 100+ objectives. It's an incredibly intense and busy day, and if you haven't lived it, you really can't appreciate it.
And as I said, I have the legal responsibility for a sibling with a disability, as well as taking care of a mother who is in severe decline mentally and physically. And I have a husband and children who need my attention and care. And now and again, I would just like to have a couple of hours where I could just think about myself. But I spend between 50 and 75 hours per week on classroom related activity, because I LOVE my job and I LOVE my students.
So - as far as your particular situation is concerned, knowing first hand the stresses of both family and of teachers - I would not make a judgment. As I said, if I even take 3 minutes of time during the school day to write a note to each parent, I have spent 30 minutes of my instructional day, which is 30 minutes that I am not teaching anyone. (And time yourself - you can't write much in 3 minutes, especially if you are supervising 10 kids with special needs at the same time.)
I do try to give the benefit of the doubt to the families of my students when they are not exactly considerate or politically correct in their communications with me. I also try to do the same when the residential and adult programs involved with my sister communicate. We are all human, with lives outside the immediate moment, and none of us is without fault. So perhaps, when you are able to communicate in a calm and unemotional way, you could ask the teacher to clarify what she meant. Try something along the lines of "I understood you to say that I shouldn't make waves because my son's IEP was nearly taken away. Is that a correct interpretation, or did I misunderstand?" And please be open to the possibility that you did not understand what she meant. Life is full of miscommunication, even between people who know each other well; communication is a two-way street, and both sides need to keep the roads open.