Thing is, I reckon this Horowitz bloke is just having a rant because he's had writer's block
Tolkien managed to stack up the bad guys without resorting to anything that even today we might get offended at - if anything he was the very model of 'PC'! Possibly by, as Hookbill says, portraying his evil in a very third party way, through the minions, the
results of Sauron's works. On the other hand, Philip Pullman (for one) doesn't appear to be bothered in the slightest who he upsets - having an evil woman (sexist!) and an evil priest (irreligious!) in his most famous work.
So there are just two examples which put paid to the ill-founded rant.