Tut. It was "a big Amarone" in the book, which is a far more suitable pairing, but few had heard of Amarone in the early 90s so it got dumbed down.
Oh I fucking love Amarone! It's amazing. First encountered it last Christmas. Much more suitable for pairing with liver than Chianti, as you say.
Actually there's a subtle pharmacological joke in the film. Liver, fava beans and Chianti are all rich in tyrosine, which can cause unpleasant and even dangerous symptoms in humans but is normally metabolised by an enzyme called monoamine oxidase (MAO). However, MOA inhibitors, used as antidepressants and mood stabilizers, stop MAO from being produced, which makes you vulnerable to tyrosine, so there are certain foods and drinks you're not meant to have if you're on these drugs. I think nomadologist pointed this out here, years ago.
So Hannibal Lector consuming these things is a way of showing that he's come off his meds. (That, and the fact that he's murdered and cannibalized someone.) But the choice of Chianti is not an 'arbitrary wine most people have heard of'.