If someone doesn't care one way or another, the label is useless. If someone has a positive opinion, the label helps the consumer seek it out. If someone has a negative opinion, the label helps the consumer avoid the product. If they fight against labeling it is because they consider that the third group is or can become bigger than the second.

The generic arguments against that sort of thing are distortion when the category boundaries are a bit off from where they should be, and overhead where any time you do anything there's extra compliance paperwork and delays.

Overhead in particular can be rather stifling. For example environmental reviews for large projects have reached a "the process is the punishment" level of overhead.

Eats into profits and increases accountability.

I believe they prefer the term “pro-business.”