We understand, we just don't agree with the way in which you going about it. Furthermore, just because people may disagree with you, does not automatically make us management either.
With regard to the main point you are making, the company has simply stated that pilots are not conducting single engine taxiing AND are not giving any reason in the post flight report. They have no issue with you not following this SOP, providing there is a valid reason. So in short, shut down one engine OR make sure you explain why you didn't.
Do i agree with the threat of termination because of this? No. This is however their train set and they get to make the rules.