What Tolkien does in the book is set up an almost all-evil Gollum from the get-go. Then, gradually, we see some possible tiny glimmers of redemption and hope in Gollum's character - which go completely over Samwise's head but which Frodo affirms.
The great thing is, Tolkien - in his capacity as omniescent detached narrator - allows us to feel empathy for Sam's suspicion and fear towards Gollum - Sam is motivated by his great love for Frodo, and of course we can appreciate that Gollum is a very dangerous and unpredictable character. Sam's feelings are entirely understandable.
And yet a wise reader can also see that Frodo has the far greater and deeper wisdom here. The principle of Mercy - a higher principle in the universe than brute force - is at work, and Frodo affirms this.
I wish to God that PJ had shown this crucial aspect of Frodo's character, I really do.
Quote from Frelga
... and I am still mad that PJ stole his near-redemption on the stairs and allowed him to split Frodo and Sam.
Of all PJ's changes, I am most saddened by this one.
It's very well acted, but ... it breaks my heart, and not for the right reasons.