Westphal got fired because he was a terrible coach and the entire locker room hated him, not just Cousins.
I don't think that's the case. Westphal got fired because he had an extremely public falling-out with Cousins. Westphal effectively forced the Petrie FO to choose between the two. Now, it's fair to say that Westphal was to blame for the situation, but it also seems likely that without Cuz on the team, Westphal served out the season.
Whether deserved or not, Cuz got the reputation of a coach killer, to the extent that he has such a rep, on the basis of Westphal.
Cousins' history has no bearing on my opinion on the current subject, but denying that it is there seems to be arguing from a false premise.
As far as the current subject goes, I think it is far too weakly sourced to worry about. Citing vague "perceptions around the league" is pretty much admitting (in my eyes) that you're working with nothingore than cow patties. Just remember all these vaguely sourced things we've agonized about that didn't happen after all...Brady Heslip and the nonexistent ten day contract; Josh Smith and the Pistons lighting $40M on fire because they obviously couldn't trade him to us; Deron Williams and the oh-no-we-were-actually-after-Plumlee false rumors. To me, this has zero credence as even being a rumor at this point.