The RIAA and major labels are one and the same. It is disingenuous at best to try and distinguish one from the other, when the board of directors consists entirely of label representatives.
Meanwhile, precious few artists whine about piracy like the RIAA does, you hear a lot more whining about the labels, because they're the ones screwing artists.
The RIAA represents WMG, UMG and Sony Music. Each of those has a bunch labels. They themselves are not labels. For instance, WMG corporate has no A&R staff.
The business of music is different than the practice of it, and lumping it all into the "label" itself is disingenuous. The politics within those companies usually means the labels at the very edge (where marketing and A&R are) are often at odds with corporate/RIAA.
When I'm on better a better connection I'll post some examples.
I don't mean to be pedantic about it, but the ecosystem around music is much more complex than "sue them all"
Division, brand, subsidiary, however you want to spin it. Common ownership, common responsibility. An entity cannot be "at odds" with a parent entity, such an assertion would be laughed out of court. Internal politics don't matter to the outside world.
Meanwhile, precious few artists whine about piracy like the RIAA does, you hear a lot more whining about the labels, because they're the ones screwing artists.