In the various forms of support I've done, I've always encountered rude customers at some point. It's the job. If you feel like you have to be defensive (per other comments here, it sounds like this isn't the first time), you shouldn't be responding.

> I guess I've vented at support before, but usually in a tone that I hope better acknowledged that it wasn't the agent's fault.

I had a very bad experience with Chase. (They took $900 without explanation, and still haven't returned it) In my many calls, I had some heated venting sessions. I usually at least once told the person it wasn't personal, but they were the Chase rep at that moment.

As an aside, responding to this thread with a throwaway created during this thread, everyone is going to assume you work for Ghost.