One observation here: the Old Forest trees enmity illustrates a depth brought to Middle-earth which PJ's movies missed, that there are autonomous forces for good and ill operating. Earlier, Gildor says:
"The Elves have their own labours and their own sorrows, and they are little concerned with the ways of hobbits, or of any other creatures upon earth."
And later Aragorn and Gimli about Caradhras. Aragorn:
"There are many evil and unfriendly things in the world that have little love for those that go on two legs, and yet are not in league with Sauron, but have purposes of their own. Some have been in this world longer than he."
"Caradhras was called the Cruel, and had an ill name," said Gimli, "long years ago, when rumour of Sauron had not been heard in these lands."
Middle-earth can be doubly treacherous, then. It is more then a matter of watching out for Sauron's agents. There are unsuspected and unplanned for agents for good and ill, perhaps operating independent of others, which is in a way more realistic and gives a feeling of depth to the world.
And, of course, it gives Tolkien the first of his chances to have trees react to two-legged "aggression".
