To me, a lot of people are missing the heart of the issue. Kirk Ferentz created a culture that was insensitive to black players, over years. Doyle or Brian Ferentz did not institute the unwritten "rules" of dress, music, hairstyle, social media that defined how a "proper" Iowa football player looked and acted, and was clearly viewed as uncomfortable by black players. These standards became the foundation of Iowa football over years.
It is the literal definition of institutional racism and 100% lays at the feet of Kirk. It is his program.
Once you have created a program that is systematically racist, no one should be surprised that outright racists like Doyle (and maybe BF) feel protected and empowered to enforce the cultural rules against black players disproportionately, and may cross the line frequently.
Because of George Floyd, former black Iowa players now feel comfortable in holding a mirror up to Kirk Ferentz and the Iowa football program, asking that they finally acknowledge the institutional racism that has existed over 2 decades.
I personally don't care if Kirk is let go or not, he is not for long anyway. The one fact that would change my mind is if the players (or parents) have text or email evidence that this issue was raised with him in the past, and he is caught in an outright lie that he was ignorant of the culture he himself built.