Sherman actually hit his teammate Bobby Wagner, but odds are he was aiming for Mariota.
The Seahawks and Titans brawled after Richard Sherman was flagged for attempting to hit Marcus Mariota out of bounds.
Mariota was scrambling to his right while being chased by Bobby Wagner. Sherman came in and launched toward Mariota, though he ended up making contact with Wagner.
Titans offensive lineman Taylor Lewan rushed to Mariota's defense and a scrum broke out. In the end, both teams were hit with two personal fouls each, so the penalties offset.
I understand the rule, but it still feels wrong that the Seahawks weren't penalized for Sherman's hit, which was really dirty.