What? Can they possibly be that stupid?
I find it very believable that they could be that ignorant, especially considering the timeline. Griner committed to Baylor as a sophomore. Her father did not accept her as a lesbian until after she began attending Baylor. Why would he research Baylor's policies on homosexuality to any great degree? And I wouldn't expect them to have general knowledge about Baylor policies. In their perception Baylor was probably primarily a Texas school that played DI sports in the Big 12, not a religious institution.
If think her father's comments are reflective of a lot of families going through the recruiting process who are making decisions about colleges based on various limited information. These parents and family members never went to college themselves so they have nothing in their own experience to draw from. In many cases haven't traveled very far in their lives and have a more limited knowledge base from which to draw on. At least at this point the family members still don't have computers and internet access sitting at home to research. They have what the college coaches are telling them, what their high school and AAU coaches tell them, what some brochures tell them, and maybe a dog and pony show of a campus visit.