People who expose this behavior by a vet, because otherwise most people will never know who they are trusting with their horse, are not responsible for a decision the vet makes later to unalive himself.
The number one rule for the survivors - Nothing you did, or did not do, nothing you said, or did not say, caused this decision. This is a decision someone made for themselves.
There were other options for this person to act on. A change of careers, perhaps addressing some mental health concerns, etc.
The public needs to know that someone they trust with their animals is not trustworthy. With their day-care kids, with their elderly needing in-home care, in their nursing homes … etc.
It is up to the untrustworthy person to fix the unfortunate damage they are doing by reaching out for help, by taking positive steps in the right direction.