(Note: The company called Rainmaker Entertainment today is not the same organization I worked for; that part was sold off. Also, the other studios in my history aren't part of this rant -- some of them being union shops probably has something to do with that.)
Here's what all the fuss is about:
If you've just seen the headline/image macro version of the story, it might have come across as, "Some Animators Didn't Get Credit On Sausage Party," and you might have thought, "What's the big deal?" because there's a couple of misconceptions about screen credit:
1. Lots of people get left out of the credits. If they put everyone in there, credits would be impossibly long!
Check the credits of any Pixar or DreamWorks film for all the tangentially related HR/accounting/security people included. Inclusion is default. Removing credits is a deliberate decision. Space might be an issue in big VFX movies with multiple VFX vendors (Matrix, Batman, etc.) where each VFX studio gets a certain amount of space, but an in-house animated production pretty much has only its own staff to credit.
Probably they were so consumed with laughter over how hot dogs kind of look like penises, they just forgot.