Psychiatrists aren't supposed to be helpful?
Wow!How profoundly retarded!

Psychiatrists aren't supposed to be kind and helpful - that's for psychologists and counsellors. They are clinicians. Psychiatry is actually quite a dry profession, conditions of the mind are viewed as you would a condition of the body and are treated as such.
Granted, even a physician finds a good bedside manner to be helpful in plying his trade so this would apply equally if not more so to a doctor of the mind

Absolutely, re: respect. But I don't think he so much turns off his psycho side. When he treated patients, it seems it would have been a) a not terribly boring way of making $ b)a n intellectual challenge for himself, and c) a great way to "hide in plain sight."
Often those with inner conflicts & traumatic experience will go into psychiatry to better understand themselves.
As far as the politesse, it is quite clear that Lechter thinks of himself as a refined,superior, cultivated, civilized person. He appreciates politeness and finds the regular rough and tumble "distasteful" vulgarity if you'll forgive the pun.

Lecter likes respect. He can shut off his psycho side to be a functional human on the personal side. Sociopaths are very good with that. The BTK killer was notorious for that.
Lecter was very respectful to Barney and Clarice because they showed him respect.
((Damn the remakes, Save the originals.))

he could pretend to be kind and helpfulif pretending was good enough for his patients or not is another matter.

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In the film he actually goes to the trouble of finding that one murdered patient who he apparently was attempting to treat properly though it 'was going nowhere'

I Agree with that totally, I can imagine his voice and his mannerisms really relaxing you and drawing you in so you feel totally comfortable with him treating you ,
I was waiting for my hearse what came next was so much worse

I cannot picture him being kind & helpful to anyone though, can you?
Yes. Hannibal for all it's flaws had some moments of him being charming and helpful.
Let's be bad guys.

Lecter could be kind and thoughtful if he had some level of respect for a person. He goes from taunting Clarice to being quite helpful and even warm with her once he realized that she's worth talking to. In fact, Demme told Hopkins that the reason he was considered for the part was because of his performance as the kind Dr. Treaves in
The Elephant Man
, implying that he did want to see the better side of Lecter's nature in some scenes.
As to the patients who he didn't find interesting or worthy, Lecter was probably practical-minded and professional enough not to torment them, at least the ones that he didn't intend on killing.

I've met doctors who would not immediately bring "kind" and "helpful" to mind. Didn't mean they didn't do their job well.
Glasgow's FOREMOST authority
Italics
= irony. Infer the opposite please.

He is smart and cuts right to the heart of someones problems instead of floundering and guessing. That is certainly a useful skill.

Eh, watch Mads portrayal on the TV show. Maybe not kind, but logical and clinical, which can help too, I suppose. Hannibal is good at getting directly to the issue, whether with his mind, or a knife, depending on what he's doing.