I agree the the *best* way to learn from literature is to be exposed to it when you're mature and open-minded enough to 'get' it.
But I don't think a person is necessarily ruined by early exposure. For example, I used to watch "Rocky & Bullwinkle" as a young kid, and I liked it on a little-kid level. I saw it again as an adult and got a lot more out of it...all the political nuance, the double entendres...great stuff!
Had I watched a cleaned-up version as a kid, it wouldn't have mattered at all. The more 'advanced' stuff went over my head anyway.
Yeah...I just kinda equated 'Huck Finn' with 'Rocky & Bullwinkle'...