The hobbits made the trees in the Old Forest hostile. Here's how I know:
Tolkien wrote in one of his letters:
The 'attack' of the trees of the Old Forest was just natural
growth: the reason the Old Forest is queer and hostile while
the Lothlorien is beautiful is because the Old Forest was
chopped down and burned, while Lothlorien was loved.
Just a note. It would also explain why Fangorn feels the way it does: it was neglected, and avoided.