Dr. Loomis from Halloween. Your thoughts?

In the movie Halloween (1978), Michael Myers kills his sister when he's just a child, btw spoilers. He is obviously sent to a mental institution, and the man assigned to his case is Dr. Loomis. Here is a direct quote from him, later in the movie.

I met him, 15 years ago; I was told there was nothing left; no reason, no conscience, no understanding in even the most rudimentary sense of life or death, of good or evil, right or wrong. I met this... six-year-old child with this blank, pale, emotionless face, and... the blackest eyes - the Devil's eyes. I spent eight years trying to reach him, and then another seven trying to keep him locked up, because I realized that what was living behind that boy's eyes was purely and simply... evil.

And also, he spends the entire rest of the movie trying to find and kill Michael Myers, with a giant revolver. Without knowing anything about therapy, I assume this is considered poor medical practice.

But seriously, is that sort of fatalism about a patient considered a faux pas in your field? Should he have kept trying to reach Michael emotionally, or is it accepted that sometimes someone is walled off too deeply?