Frodo, punchbag of the quest?
I do not feel he was a punchbag because he was attacked by his enemies, for anyone else bearing the One Ring would be worse. As for Mr. Carter's statement(s), I disagree with him. I had heard somewhere else too that "Frodo's Weathertop wound was kinda his fault," and that he deserved it. His wound on Weathertop, more than a punishment, to me, is a process of him and his companions becoming something else. Yes, he was weak, and not strong enough to resist the Evil; but without that "folly" would the quest have been achieved? I doubt very much. After this wound he resisted all Nine alone and proved himself to be the best Ring-bearer. This also helped his friends to understand the real weight of the quest.
Shelob thingy-- how is that over-confidence? His trust in Gollum is what Mr. Carter considers his over-confidence? Or his decision to go into her lair? If I remember correctly, Gollum had told them there was no other way, did the hobbits have to go another way without knowing anything and getting lost in the Enemy's land? How?
His failure on Mount Doom and later his suffering is a punishment? I always saw it differently. I felt Frodo was rewarded with the most precious gift by going into the West. Souron and Gollum suffer terribly because of the Ring, unlike Frodo who suffered least as compared to the other two. If he were weak, he'd be punished, not rewarded. Reward and punishment is respective thing. What I see as reward, in this case, someone else may see as punishment. His wounds and sufferings, like everyone else's were the sign of his bravery and self-sacrifice, instead of deserving.