Considering that a sane person would just find someone else to offer the dish to, I concur, unless Sam has an ulterior motive.
He's like a drug-pusher?
Not meaning to be a Knight Templar, but aren't you reading somewhat disturbing meanings into a children's book? I always sort of saw it as a story with the moral that "you won't even know if you liked something- until you actually try it yourself!" Granted, Sam does carry on with this more than a real person probably would, but how else are you going to fill a book and get all those rhymes in? Again, not meaning to be overly zealous, just saying.
Sam is that annoying kid from school who would neverstop talking to you!
Sam is trying to get Sam-I'm-Not to accept the part of their food supply that was dyed green in a storage accident, so that he will be able to survive until it's safe to leave the bomb shelter.
Am I the only one bothered by the warped aesop?: "Hey kids, if you're trying to get someone to try something, keep pestering the person until he or she gives in!!"