I believe therapist are human like doctors, like anyone else. Therapist's have mental problems, marriage problems, problems with their children, inlaws, parents, the list goes on. They have problems that change with their life just like everyone else.

I do believe that most therapists try not to take clients where they can't be objective. One of prof who is a T, while he was going through his divorce, he didn't take marriage couples or individuals who were going through it. My own T now won't take DID clients if he can help it, because he is too vulnerable to their demands. If we had to wait for all psychologists to be perfect, there wouldn't be a profession. The point is everyone has issues and problems, T's are not super human by any means.
My T says that an effective therapist is one that has been %#@&#! up at one time or another.

As far as doctors, I think a heart surgeon can be an effective one if he has heart disease. People who get into the profession as helpers, have problems like everyone else or they will encounter them as they get older. There is no way to prevent it. It is easier for one to help others than it is to help with their own family, there is no objectivity. A therapist isn't directly involved with their clients so they can keep a objective distance.

But I do think overall they need to be strong to do the demanding job. I would like to see therapists take a break or something if they are suicidal or dealing with personal issues that effect their job.