You assume correctly.
The reason I picked "the person" is because that makes it easy to comprehend the stance on the matter.
Even if a book is completely racist, as long as it is fiction, it says nothing about the writer or his opinions.
Nobody reads Silence of the Lambs and thinks that Harris eats people.
Edit: obviously autobiographies, etc. are something completely different.
James Joyce, in Ulysses, wittily deals with the error of assuming that the attitudes of a fictional character equate to the attitudes of the author.
"— You don’t know yet what money is, [Mr Deasy said]. Money is power, when you have lived as long as I have. I know, I know. If youth but knew. But what does Shakespeare say? Put but money in thy purse.
— Iago, Stephen murmured."
But the point is not just that Shakespeare doesn't encourage us to "put money in our purses"; he stigmatises this materialist sentiment by placing it in the mouth of one of his cruellest villains. We know that Iago is a liar, so we might be suspicious even when he offers what seems like sound advice.
Basically there are three issues to be considered:
1) Fictional characters and their opinions (which an author and the text s/he produced may or may not endorse).
2) The writer and his/her opinions (in my opinion basically unimportant; Joseph Conrad has been dead for nearly a century, Shakespeare for four centuries, while their works and the characters they created can be bought or borrowed and read tomorrow).
3) The book and its opinions, derived from a close reading of the text and its implied attitude to the characters and situations as expressed through literary style and symbolism.
I'm not interested in "the writer or his opinions", and I'm interested in the characters and their opinions only in so far as they help me understand the book and its opinions. When Achebe said that "Joseph Conrad was a bloody racist", he didn't mean that the actual writer, who died in 1924, was racist; he certainly didn't mean that the characters expressed racist attitudes; he meant that the values and implications embodied in Conrad's book, Heart of Darkness, were racist.
Similarly, while no one thinks Harris eats people, one can assume that Silence of the Lambs embodies an attitude to Hannibal Lecter and, by extension, to his crimes. Books embody an attitude to the events they describe by definition.
An obvious example that takes us back to Shakespeare. Macbeth (the play) is a story about Macbeth (a character) who is a usurper and a tyrant. Only an idiot would think that this means that the play is in favour of usurpation and tyranny because its protagonist does these things. In fact the play is very clearly anti-usurpation and anti-tyranny; this is clear because:
1) Macbeth's usurping the throne leads him through agonies of guilt and despair to a sticky end.
2) He is tempted to kill Duncan by diabolical forces (the witches, and Lady Macbeth, who explicitly pledges herself to evil spirits).
3) He is associated consistently with imagery of darkness and night, directly associated in the play's dialogue with evil.
4) He is contrasted with two virtuous kings, Duncan (whom he kills), explicitly associated with angels; and the King of England (the historical Edward the Confessor) who is attributed with the miraculous power to cure disease.
5) Shakespeare actually suggests that natural phenomena protest at Macbeth's usurpation: "The heavens, as troubled with man's act, / Threaten his bloody stage: by the clock, 'tis day, / And yet dark night strangles the travelling lamp." Which is to say, killing a king is not only bad, but unnatural; the very structure of the universe protests at it.
In other words, through his portrayal of what happens to a usurper, through the web of imagery, incident and characterisation that he creates, Shakespeare crafts a play that is strongly opposed to rebellion against lawful authority. Needless to say, in the early seventeenth century, at a time when criticising a king could have extremely dangerous consequences, it would have been difficult for him to do otherwise; indeed, the portrayal of Edward the Confessor, and the implication that Banquo's descendants will be kings "to the crack of doom", were transparently intended to flatter the reigning monarch, himself a Scot who had inherited the English throne.