We are implementing a new system at work. It's a huge change; changing over from an older system. It has been in the pipeline for 2 years. Three of us have been working on it now for about 6 months. One part of it involves introducing a whole new set of servers to host the system. This is a complex piece of work. The servers have to be available 24/7. We had described the architecture of the system on an internal website. We had discussed it over a period of several months with our manager. We described why we had made some decisions over others, trade offs we had made, etc. We had explained everything and documented it, and our manager was in agreement with the decisions we made.
In a broadcast e-mail, we shared this architecture with a wider audience. A recipient of this email discovered what he thought was an obvious flaw in what we were doing. This person is part of our group (we have the same manager), but not involved in the system migration. The supposed flaw was identified in our documentation, and we described in detail why we made that decision. The person then e-mailed us about it, but crucially copied our manager. This - in our estimation - was a cynical attempt to curry favour with our manager, while simultaneously trying to undermine our efforts. We had no problem with the problem being identified, but there was no need to copy our manager.
Our manager then, instead of saying 'Great thanks for that - I will discuss that with the team on Monday', invites them to redesign what we have come up with even though he already signed off on what we had done. We defended what he had done and the decisions we made in a reply email - he never engaged or bothered to replied to that. He now wants us to work with our erstwhile critic. We feel that our manager has undermined our efforts. He doesn't trust us to get the job done, and is willing to swap us out whenever necessary. There are going to be other more vocal critics later in this migration. We wonder if he will also assume that we made the mistake, and side with the person making the criticism.
He would probably say he has a job to do and he doesn't care who does it, but he is also managing a team and you can't replace one members efforts with another like changing parts on a car. A good manager should always defend the team no matter what, whether the criticism comes from within or without.