Jonn - I believe the issue is that everyone has a different definition for what "valid criticism" is. As John tries to articulate below is that a lot of us believe those who regularly criticize the FO and managers sit firmly atop Mount Stupid. Even when others try to introduce another point of view, or try to justify the thought process, it's often met with loud opposition. Although you suggest you like to hear other peoples opinions and reasoning, that isn't the case with everyone. As is VERY common in society today - most people become anchored to their opinion, unwilling to admit they might be wrong (or even less right) and thus even in the face of new information, they put up their shields and choose to fight instead of listen. I really have no issue with people developing opinions - I just think in most cases, they shouldn't be so firm on them - as they should acknowledge there's probably a lot more information they aren't privy to.
This team is 2 wins away from their first World Series win in 32 years and people still believe that's in spite of the FO and Manager. I suspect if the Dodgers end up winning, there will be LOTS of people who blame that on Shatkins and Schneider and suggest they should lose their jobs.
I've been alive long enough to realize nothing is going to change - people are always going to be like this, but I often find that disheartening.
Obviously I enjoy supporting the FO/Manager and try to see that most of the decisions aren't anywhere near as clear cut as some suggest. I also don't expect them to be perfect - they are human and make mistakes. I choose to be more supportive than not, but understand most take the opposite approach. I also know that at times, people are just venting out of frustration and I should just let them do that - instead of poking them.
I hope that helps.
My last thought on this is that while most people rip on the tactical decisions, I do think Schneider deserves a lot of credit for the softer side of the job. I certainly appears he's created an awesome environment for this players. I don't think you become such a resilient group without strong leadership in the clubhouse. I don't really know how much that stuff matters in comparison to lineup, bullpen and substitution decisions during a game, but there's certainly a possibility that John's biggest strengths are things we don't see on a daily basis.