Revelations and Realizations

[The Saucepan Man]

Tolkien didn't even LIKE Shakespeare and he felt right cheated by Macbeth, especially the Birnam Wood business, which, as we know, was one of the reasons for the Ents, i.e. what if Birnam Wood really did come to Dunsinane?

I am not sure that Tolkien had a wholesale dislike of Shakespeare, although the line from Macbeth which you refer to certainly irked him and was the inspiration for the Ents' march on Isengard.

Whatever feelings he may have had with regard to Shakespeare's works, however, it didn't stop him nicking and adapting for Aragorn the "All that glisters is not gold" line from Merchant of Venice.