RR produced a film in 2015 based on his sons life and multiple drug rehab attempts called Being Charlie. His son was the screenwriter.
The character doesn't come across as particularly sympathetic and even says so in the film
https://www.independent.co.uk/news/world/americas/crime/nick-reiner-rob-being-charlie-b2884818.html
Interesting insight into how his son portrayed the psychiatrist visits to his parents
"...Being Charlie is about the tensions between Mills and his parents, who are desperate for him to get clean and insist he checks into rehab on the advice of counselors, despite his insistence that he does not find the treatment helpful or conducive to recovery. The film attempts to address both perspectives in the interest of helping other families facing comparable situations.
Rob Reiner told The Los Angeles Times upon the film’s release: “When Nick would tell us that it wasn’t working for him, we wouldn’t listen. We were desperate and because the people had diplomas on their wall, we listened to them when we should have been listening to our son.”
“We were so influenced by these people,” Michele Reiner added. “They would tell us he’s a liar, that he was trying to manipulate us. And we believed them.”..."
So they chose to believe and stand by their son.