But it is an understandable reaction - it can be understood. I do not draw my personal line in the same place as the OP (I already play in Open & have never pledged for a start, I also do not think this is the beginning of a slippery slope) but I can empathise with their concern and hope to reassure them that the sky is not falling
I'm in favour of this because of the PvP aspect. It potentially allows a release of tension within the community, but as this thread shows it still comes at a cost. I'm sure you are familiar with many such compromises that have not gone the way you had hoped, and while you are not considering a refund for those choices you've probably had the 'you bought the wrong game' argument levelled at you (not by me). This situation is analogous, albeit with the important difference that the OP bought the right game, and now the game will potentially change to one they would not have bought had it been the proposed way at the time of purchase, regardless of how long ago that was.