Also, this law firm should be punished. The image is clearly not libelous. Libel requires two things: 1) to be a factual assertion rather than an opinion, and 2) to be made maliciously rather than as commentary, review, or satire. This image clearly does not support either.
These lawyers have sent out the letter in an effort to get the content removed. They are representing themselves as lawyers while doing it, and alleging that this sort of thing is against the law. It is not. The lawyers should be sanctioned or disbarred along with any other lawyer who wields the power of the law in a knowingly incorrect way. Lawyers have the legal right to act in a specific capacity; in exchange, they should also have the legal responsibility not to abuse their power. This is not merely wrong, it is frivolous. There is prima facie no evidence.
Furthermore, even if this image was somehow libelous, they're sending the C&D to the wrong person. Owners of communities are not legally held liable for the content created by their users. The users are. The C&D should be being sent to WaffleImages.com, which is an image hosting site, or it should be sent directly to the person that uploaded the image. Courts both in the US and abroad have repeatedly ruled to this effect.