I see no reason why the Yor should be considered evil and have tried instead playing them as "Benevolent"
But yeah, the cost of Manufacturing Population is too high early game, so you need the boosts the Benevolent tree provides to compensate.
The AI seems to struggle with the cost as well, in every game I play with the Yor as an opponent, they're always way down toward the bottom of the power rankings. As are the the 'evil' races overall, in general. Is that because the Malevolent ideology tree is the worst (it is) and/or because the way the AI plays evil races, and plays against them? Lots of wars, few trading partners etc?