Owen,
Situations like this happen from time to time, and it could really be about anything, this one is about transponders. My advice to you is turn this into a teaching moment not just for yourself, but the controller also. It is very easy to get caught up in the moment and get defensive or try to argue your point, but at the end of the day was it worth it? You received a 48hr ban for not hitting a single button? I mean come on dude!
I have been sent contact me messages many many many times before where I was flying VFR and the controller thought he needed to talk to me. What did I do? I contacted them!! If it was a ARTCC I was familiar with I would kindly hop on the TS, find the controller, and have a nice conversation about what I was doing. 99% of the time the controller learns a lot from it, and supervisors aren't called. If you are not familiar with the ARTCC just simply file some feedback for that controller for the ARTCC staff to review, in the meantime comply with the contact me requests to be on your way.
See my point? It's kinda silly in the grand scheme of things.