I think you had it coming .. as many may have pointed out already, the first response from the CSR was "to the point" - i.e. you asked a specific question - and you got an exact answer.
Maybe you didn't like the answer.
So, you resorted to using uppercase words (TERRIBLE).
And you were not given a NO for a service request - you had a question for which the answer was, rightly, NO!.. What else do you expect - a No with an apology attached?
Ideally, you should have responded to the CSR's first reply with a "Thanks for your response ... I would suggest you to strongly consider .. <blah> as it is already a norm and most competitors offer this ... " etc.
Instead, it appears that you took offense ... and well.. it was just downhill for you from there wasn't it :)
I also think the CSR didn't step out of bounds any time ... if this thread is reviewed by his supervisor, he/she would probably get a certificate of appreciation for handling an irate customer.