I suspect that what happened when Dylan wrote that song is this.

1. He read the one very sensationalist article where he got all his "facts" (and it was full of inaccuracies). He believed it, and he based his song on his immediate gut reaction to what he had just read. Perfectly understandable on his part.

2. He looked no further than that. He had a great song, he no doubt felt strongly about it, and he went with it.

I can't fault his artistic instincts when it came to writing "Hattie Carroll", and it's not surprising he would have believed the article, because it met any idealistic 60's young radical's expectations perfectly. It provided the perfect victim and the perfect racist perpetrator. I'd have believed every word in it too at the time, no doubt. He probably should have read a few more articles about the incident after that, though, before going ahead and recording the song, because it could have come back to haunt him if it had gone to court.