How about doing this to every pizza store you encounter that serves meat?
You're not profiting..just wasting a business's resources by misrepresenting your identity and intentions.
Just because you intend to use the 911 hotline as an emergency resource surely shouldn't impede my right as a phone owner from calling it in the manner you intended. It's my god-given right as a phonebook owner to call whatever numbers I see fit in whatever quantities I want to.
It doesn't even have to be 911. You can DDOS the phone lines of any business to make them less effective. Is this ethically defensible?