I don't think warned people against marraige, he himself was a married Catholic.
People who say he was racist are just wrong. He wanted to create a mythology for England, 'cos they didn't really have one of their own ( check the facts, King Aurthur is a Welsh legend before the English nick him, Tolkien would have been well aware of this). As such, It would have been fairly hard to create a black/Asian charachter to fit an ancient/ near medievel english myth.
Anyway, back to definition, he was a writer who created the second highest selling book ever ( the first being the Bible), and a very good book it is too, the only people who say it's boring, are the ones who never read past the bit with Tom Bombadil.