You have right to political opinions, but as teachers have long known, they come with a caveat. Schools regardless of level are hyper sensitive to political opinions that appear negative or are counter intuitive to the educational mission. I am pretty sure Bobby like most public education employees are required or asked to sign a document affirming such an understanding. Most institution ask their employees to be clearly differentiated from the role as an educator or coach, and when that cannot be clearly disseminated they you need to clearly state I am making this opinion as a private individual. That is principally why you see on most educators twitter and social media accounts "Opinions are my own and not my employer."
But in all honestly, Bobby wouldn't have run afoul of the University on his Arntzen opinion had it not been attached to that god-awful letter. Had his name appeared on a full page of names supporting Arntzen little likely would have happened. The letter was anathema to just about everything the University espouses for its students and athletes. Worse it was the same anti-liberal trope gussied up for the 2021 crowd that had been bouncing around all levels of academia since the 1960's.
As a career educator, I have heard anti-progress criticisms much of the last 20 years whether it be common core, creationism or intelligent design, and sex education. I have attended board meeting after board meeting where parents and community members have railed about liberal conspiracies and brain washing by liberally trained educators. Always clamoring for local control and resistance to national change, but what is absolutely true and mildly ironic about Montana and Idaho where I have spent most of my educational career, few states have granted as much local control to school boards and administration as they have. What this is functionally a collective ignorance by parent groups about how local education policy and curriculum is adopted.
Curriculum is mandated by the state, but districts are free to interpret (especially in Montana) about how they are meeting those standards. You can (per my experience) merely craft a document that matches those standards and from there your local education agency adopts those guidelines and teachers are frankly pretty free to interpret what to teach, how to teach and when. Since there really isn't a follow through on what absolutely must be taught beyond the Smarter Balanced Tests that focus on leveled Math and English level examinations that focus on cognitive skills rather than rote memorization of facts, its hard to even imagine where groups come up the crap they do outside of their own imaginations. Most parental groups that have cast aspersions upon the districts that I have worked in haven't spent a single minute inside a class room and seeing what actually goes on. My goal is to focus on best practices to get the most of my students as I can regardless of ability.
Letters like the one penned in support of Artnzen are laughable in as much as they are offensive. If they really knew what we were expected to do, with the resources we have, and the time we have you'd laugh at the letter in the same way I did. We just don't have time to focus on the petty BS they are always claiming we do. Indoctrinating students takes a ton of time and concert with a lot of people, and I don't have enough hours in the day to do that shit.