How would you measure mental health harm? Suicide rate by job?
Intimate jobs like dentists, doctors and vets have high suicide rates. Jobs that stress people's bodies like construction workers and farm workers have high suicide rates. Jobs with exposure to violence like police and military have high suicide rates. Jobs with high chemical exposure rates like chemists and manufacturing. These kind of jobs have risks. Sex workers tend to deal with the first three.
Should we start banning jobs based on mental health outcomes? Or should we just make sure whatever jobs people have they are treated with respect and recieve the healthcare they need to function. What we should be doing is making sure such jobs are conducted as safely as possible for everyone involved.
The supposed "concern" about sex workers mental health without concern for similarly mentally stressful jobs is usually a sign somebody is actually operating from a bad faith position about how sex work is "icky".