If what you say is true, Danny is supposed to figure out how Daniels fits and interacts with 7 other players? No GM can do that! Both guys have their warts, but their "attitudes" aren't the problem its their play.
Yes, GM's do it all the time with free agents and draftees in EVERY sport.
Do you really think that it's any surprise that Nate Robinson isn't fitting into this team? The writing was on the wall that this guy wasn't the right fit mentally or personality wise. Danny ignored that. Do you think Ron Artest would have been a good personality fit here? Or Quentin Richardson? Or someone lazy like Eddie Curry or Patrick O'Bryant?
I think it's pretty clear that Danny judges talent and film but sometimes misses out completely in the extraneous other things that need to be taken into account as to whether a player is a good fit for an organization, that being personality, work ethic, personal makeup, attitude, etc. He has a decent sized list of misses in this regard. Blount, Banks, Telfair, O'Bryant, Marbury, Wallace, Daniels, Robinson, Giddens.