Brown is my favorite Celtic but I'm not sure what these "Give Brown a pass, he was hit in the head" comments are about. It's not like he's shown the ability to be a decent FT shooter at any point during his career so far.
High School, NIKE/Adidas Summits, College, Summer League, Preseason, NBA, etc. he's been a below 70% free throw shooter for his entire basketball career.
It's not a problem I think he'll continue to have, he just needs to get his reps up.