Sorry to hear about your experience with CO. From my read of the letter it sounds like your chief complaint was the way you were asked to return to coach. Many people here have echoed complaints against EWR staff for being abrasive - so don't feel out of place as you are not the first to voice such concerns.

As far as CO offering you the upgrade then taking it back - that seems like poor form on their part. You'd think they'd have their stuff together enough so that an event such as yours would not happen.

All in all, I personally do think you have a valid complaint (the way you were treated) but I don't see much that CO can do other than putting some bonus miles into your account. Might just be best to chalk this one up in the ever growing rude EWR agent column.