>The postal union is against this, usps management is against this, and business mailers are for it

I was confused by this until I realized you are missing some logical steps in your (accurate) argument.

The 2006 law took away the safety net (ie the ability to charge whatever is needed to break even).

The “you can now make a profit” rule actually made it HARDER since it came with a price cap.

It told the USPS: You can keep any profits you make, but you cannot raise prices above the rate of inflation to get them.

This forced the USPS to absorb rising costs through internal efficiency rather than passing the bill to mailers