I previously wrote that David Horn's letter was "in support of Heritage's move."
While I believe this to be the case, it was not explicit about that aspect. His letter was explicit about opposing mental health stigma, so I've updated the article to say he wrote a letter "opposing stigmatization around mental health, writing [a quote from his letter]".
Nobody asked me to make this correction. After sleeping on it for a few days, I realized this was a needed fix.