Yes, you could have deformed the outer brass fitting, but, unless you're using pliers that are too small to get a good grip around the fitting, you should be able to get it off. Do you have anything larger, like Channel-locks or Visegrips? The thing to remember is that the harder you squeeze on the outer fitting the harder it is to get it off, because you're increasing the friction between the hose coupling and the faucet spout. What you want is to be able to apply only enough pressure so that the tool doesn't slip, and no more. The only other thing I can suggest is to take a hair drier (being careful not to let the connection to the extension cord sit in water or snow!) and heat the fitting some. It will cause it to expand a small amount and it may then be a slight amount looser. And I assume you are turning counterclockwise...?