One thing Rod Serling liked to do was preach--and I don't mean that in a bad way. If you weren't around in Postwar America, say 1946 until the 1960s, you don't really understand what television was like.
Sponsors and networks killed topical television in the 1950s. They didn't want names named. Anything deemed controversial just never got on the air. Many of the Twilight Zone episodes dealt with this blind spot by disguising the message in allegory or fables.
This episode is a fine example of Serling's technique, in my opinion. He always spoke out against intolerance and bigotry and seemed to be a big fan of the "cautionary tale" approach when it came to getting his message across.
This story is a clear warning that nothing good ever comes of blind hatred and ignorance.