It was wrong to drag up whatever health problem Sifferkol has as a way of diverting attention from his comments, unpalatable though they were.
It may well be that his comments were unpalatable because he is mentally ill. I got that impression of him weeks ago. I withdrew contact, and stopped responding. Depending on the illness, it can cause harm when people confront, rile up, or argue with people suffering from mental illness. If you have good reason to think the person you are talking to may be mentally ill, you need to cut him a lot of slack. You have to be extra careful.
(I am not a psychiatrist, but my aunt was and I spent time as a volunteer working with people in hospitals, so I know the rules.)
This person apparently told the world about his problem. That is a brave, commendable, and socially useful thing to do. Dewey was right to inform us that we need be careful not to respond harshly even though this person published outrageous accusations against me and others. You would do the same thing if you learned that the person you are talking to is somewhat senile, for example, or dying from cancer. Health can affect people's judgement. We can perhaps address the technical issues he raised, but his accusations about conspiracy theories and the like should be off the table. Especially his accusations against me should be ignored, please.