With regards Dylan plagiarising music, musical notes could be compared to colours. Just because one artist may be using the same colour palette as another, the image they create will be completely different.
Different subject matter, different style, same colours.

There are greater limitations on the number of musical notes, further limited by the number of ways they can be arranged into pleasing musical passages. We can't mix notes on a palette to get an interesting shade of F.
Everything has been done before, we should judge the overall piece, subject matter, style, etc, instead of feeding the lawyers.