When "safe space" isn't

A couple of you readers commented to me that you felt cheated because the promised rant was toned down. Today I am not feeling quite as generous and I am going no holds barred.
At the beginning of our program we spent a significant amount of time creating rules that would make the program space a safe space. We then revisited those rules halfway through the program. And, I (foolishly, it seems) let my guard down and believed the organizers when they said that the space we had created was safe. But yesterday it was demonstrated to me that those rules that we had literally spent hours devising were complete fiction.
Yesterday afternoon I expressed frustration at specs that were changed late in the afternoon for our presentations that half of us gave today and that the other half (myself included) are giving tomorrow. This was a fairly significant change that obviated hours of work on my part. I first raised the issue on our internal chat channel but the only response I received were crickets. So, in my checkout I expressed my frustration by saying roughly,  “I am frustrated because…” I deliberately chose to go the direct route on the theory that I could express my true feelings in a safe space that we had spent so long creating. Turns out I was wrong.
This morning I was called on to the carpet for my “childish” behavior in expressing my frustration. I was asked “how I could have handled that better” including using the internal chat channel. When I explained that I did do that I was told it was my responsibility to ensure that the organizer saw my post. I started to mention that it seemed unreasonable to chastise me when I expressed my feelings in a safe space, but I cut myself off. I chose to end the conversation there because any illusion of safe space was gone and I had no desire to get into a disagreement in a situation where I was not respected.
As far as I am concerned, the worst outcome of this morning’s exchange is that I am now deliberately isolating myself from my fellow program members. Members that I truly enjoy being with and who bear no responsibility whatsoever for what has gone down. Despite my general frustration with this program, I was truly hoping that it would go out on a high note. Now, instead of celebrating my last few hours with friends, I am sitting in the corner, typing this blog post and dreading this afternoon’s checkout.