[Eurytus]

Actually I find this a little bit sad but not surprising. Remember that LOTR is a work of art and as such, the actual views and intent of the artist do not have much bearing upon the views of those that interpret it. Any one piece of art can elicit a differing reaction from each person that views it.
Was Tolkien a racist? We cannot say for sure although there are indications to the negative. Does this affect how people will read LOTR, no, not really.
Could LOTR make someone a racist. Again, no.

But what we are dealing with here are people who already are racist. So the question is, from their viewpoint, are there elements within LOTR that they can apply to their worldview. I think it would be naïve to say no.
As much as we can talk about LOTR being a mythology for England and hence of course people with different ethnicities are going to be seen as different and perhaps the enemy. But Tolkien’s intent about what the LOTR was going to be is not going to affect these peoples views.

Their worldview is that the white race is under attack from the hordes of non-Caucasian races. And moreover that the white race is superior.
Could they find something to back that up in LOTR?
Probably.
However we justify and whatever Tolkien’s reasons it is a fact that Sauron’s allies are usually men from the south and east. Swarthy men. Men who look somewhat like Orcs, sometimes even like half-trolls. These white supremacists are not going to take any notice of Sam’s one paragraph meditation on the enemies motives because that does not fit with their worldview. They are going to pick and mix what they want. And Tolkien does give them some depiction of men from the south and east being evil.

Can they also find elements to confirm they view of the white man as superior? Well again probably. The history of the Numenoreans gives enough detail about those of pure blood having a longer life and somehow being of a more noble mien than the lesser men. This should not be surprising considering that Numenor is Tolkien’s version of Atlantis and that Atlantis provided some inspiration to Hitler and his followers. Are the men of Gondor portrayed as superior to the men of the south and east in LOTR? Again there is just enough to give the racists succour. Often Aragorn’s kingly and noble demeanour alone is enough to quail the enemy (if but temporarily).

To summarise, LOTR is not racist. It is unlikely that Tolkien was either. But we would be foolish to believe that there is nothing in LOTR that a racist could take and use in his preconceived worldview. After all the beauty and the tragedy of art is that pretty much anything can be interpreted in pretty much anyway possible. All the more so in books.
The Bible after all can be interpreted any way you see fit, as a myriad of different Christian offshoots prove.