Wow! I have no experience with your situation. But, my first thought is this would be a violation of the ADA. I hope your HOA gets "schooled" and reconsiders their actions against you and you service dog.
Do you have lawyer?
They will get schooled...its just interesting, the management company told me the HOA doesn't want to make exception for me because it will open the door for others to try, yet when I asked about 150lb+ dogs living in the building, their response was "well, the pet policy says no large and/or aggressive breeds, it specifies your GSD as an aggressive breed, but they don't give a weight specification on large breed dogs...its so the HOA can have room to make exceptions"
Getting an attorney is not an issue, but I would rather have the DOJ (they handle ADA), HUD and my state govt. handle the legal aspects...have met a lot of people in my life, none that are excited to get into it with three govt. agencies