I mean, America has a black president now, but it doesn't mean there are no racists in the US.
This is not the correct example. At present, racists are a minority in USA.
A correct example would be:
How do you think USA would react to laws legalizing black slavery now
, laws antithetical to what most americans believe?
Most ferengi, by DS9 season 7, believed in treating women as second hand citizens and oppressing their employees.
Laws granting women equal status and employees rights would be met similarly to laws legalizing black slavery in today's USA.
As for change in ferengi values:
How long did it take for the majority of USA's population to reject racism? How many centuries?
So yes, the ferengi happy ending from DS9 is not believable.