Sorry, what did I miss? That it's from the Monty Python sketch? I get the original joke, but how it is applied here doesn't quite add up to the same situation.

It's not so much that Aragorn is a king, rather it's that an oath was broken causing the souls to not rest.

This is also ignoring that the "repressed" in this image is called "The King of the Dead", and monarchies are the butt of the original joke.