many people think so because of his early work. however, just as Mark Twain wrote stories that represented the time, so did Walt Disney write and draw his cartoons. "Tom Sawyer" and "Huckleberry Finn" would not have been the iconic stories that they are if they had been written portraying equal rights during the era that the story was set. this does not mean there was prejudice, but rather that it is a depiction of the times.
He was not a Freemason and he did not hate any ethnic or racial group in particular. His biographers do describe him as a product of his time and the America in which he grew up. That is to say, he was not as sensitive and tolerant as we would like people to be today, but his point of view was very typical of the era.