How about "Dallin, that was an asinine post, embarrassed our family, and does not reflect who we are..delete that sucker
Pronto". If Jared approved of the content, he's not the sterling guy others have said. If not, and Dallin refused and effectively said "don't tell me what to do", then that speaks to the quality of their relationship.
I have five adult children and a bunch of grandkids, so it's not my first rodeo. None of my brood are perfect, but thankfully, if I reasonably requested them to take something (even not as offensive as this) off social media, we have the mutual respect they would do so. I get it, kids aren't easy, but Dallin has taken his untetheredness to another level, and not just against BYU, but he was un-coachable which led to the early end of his NFL career.