It's the offseason, and personally, I don't see the harm in discussing (preferably in a civil manner) the shortcomings of our previous year and how we could or should improve.
The civil criticism isn't what he's referring to. That's the problem. When people call someone out for calling the head coach names, they immediately resort to "sorry I'm realistic", "sorry I don't blindly follow a coach", "sorry for not settling for Mediocracy". It that's all they were doing then fine.
People try to justify one extreme with another. I criticize the coaches and team at times but I do it without insults or slander. There's a difference.