Books to Movies: Two Towers, Is Message Really Necessary?

The heavy-handed messages in the second film are the filmmakers' choice, not Tolkien's. When characters preach in his works, which they seldom do, they talk from within their own characterizations and knowledge. Manwe and Mandos (Maiar in The Silmarillion and therefore, minor deities) act as Manwe and Mandos, not spokespersons for Tolkien. 

In fact, Tolkien appears to believe quite emphatically that since people can't know the future, they should be careful about forcing a particular futuristic outcome--and their opinions about that particular futuristic outcome--on others.

Two Towers the film does have a message: Hope is better than despair and people should fight for it. 

I'm generally opposed to message-heavy fiction. It violates the principle of show-not-tell and depending on the message, it can come across as rather trite and preachy. 

I think Two Towers (barely) pulls off its messaging for two reasons: Bernard Hill and Sean Astin, who deliver the message speeches: 

Bernard Hill as Theoden: "Where is the horse and the rider? Fell deeds awake. Now for wrath, now for ruin and a red dawn." 

Sean Astin as Sam: "How could the world go back to the way it was?"

I think the (bare) success is because of the characters who make the speeches. First, their speeches don't sound trite.  Second, the speeches come from within their personalities. Theoden is a poet warrior. Sam has a liking for poetry and a disposition to reflect on stories and their meaning. And third, the poetry of the speeches is quite lovely (and drawn from Tolkien). 

Granted, Ian McKellen's White Shores description to Pippin in Return outshines the others because it is entirely Gandalf's reflection and wish. It is consolation, not a message. And, well... McKellen! 

I personally would have advocated for Sam's speech being slightly cut or split between Osgiliath and later. Films are a visual medium. If I want speeches, I can go on social media. (I don't.)