A case could be for libel made against you for changing the intent of the cartoonist and defacing his work. I'm in the art business myself. Better remove it.
I think you mean copyright infringement and that's only if he tried to profit from it. Otherwise, nothing libelous against the artist there, however, it should be fixed...
![](http://www.readclip.com/JFK/WCR.png)
So sue me.
![Grin ;D](https://www.jfkassassinationforum.com/Smileys/DarkB/grin.gif)