Huh, wha?
If you want your populations to be less happy, start abusing them more.
I do think it should be a diminishing returns thing, with going from happy->jubilant being far harder to achieve and maintain than indifferent->happy.
Some system where the further from indifferent the people are, the greater the restoring "force" is.
To expand and exterminate -- hardly a politically correct agenda. Therefore everyone who buys a 4X game is in some way performing the acts of a villain.
Underling, “Sir we have too many Jubilant planets!”
Ruler, “Sigh, We can’t have that glass one! After all happy people just make other people unhappy.”