I have stated on here since most recent Superbowl that the firing of Steve Wilks was unfair but I never stated it was a racist firing.
It was a set up for failure situation for Steve Wilks. If a defense coordinator coaches for a head coach who made a name on the offense side of the ball, defense coordinator usually is allowed to almost 100% coach the defense as he wishes. If it doesn't work out, then a defense coordinator may lose his job.
When Steve Wilks took the job, K Shanahan told S Wilks how he wanted the defense coached and what style of defense. Not just defense philosophy, K Shanahan interfered during Superbowl and K Shanahan's meddling was a factor in San Francisco losing. I am sure during post-game analysis when K Shanahan was blaming Steve Wilks for losing the game, I am sure Steve Wilks reminded K Shanahan that Shanahan cancelled a 4th quarter 3rd down zero blitz.
The fact that Steve Wilks is ten years older than Shanahan and that S Wilks paid his dues working his way up the ranks, I am sure S Wilks knows K Shanahan is overrated as a so-called offense genius. It may have been difficult for S Wilks to talk to K Shanahan in a respectful manner.
Some head coaches can tolerate honest back and forth dialogue with coordinators. Others are thin skinned. K Shanahan has demonstrated that he is a more than decent regular season offense mind in NFL. K Shanahan has also demonstrated in Superbowls he is outclassed and outsmarted by opposing coaches.