It's not punishable because it's not technically murder unless you're force-feeding the "victim" or secretly adding rat poison to the food.  Every bite they eat is by their own choice.    Is it wrong?  Yeah of course it's wrong.  I think the law should be reevaluated to include extreme cases of feederism as a crime of abuse, malicious intent, and possibly assisted suicide without the aid of an authorized doctor.  Suicide is illegal under most circumstances.  That said, these are sick fucks preying on sick fucks we're talking about.  There's probably little to no interest in making it illegal, even though it causes damage to more than just the "victim".