Slave morality exists by taking the master morality and flipping it upside down such that whatever the master morality values as good the slave morality values it as bad and whatever the master morality values as bad the slave morality values it as good.

We're in the process of a social change where traditional master morality rooted in Christianity, Enlightenment Liberalism and Ancient Roman/Greek values is being subverted by the slave morality of "leftists" which one could describe as Secular Humanism.

The attack on beauty and the promotion of ugliness is a specific attack on the traditional moral values of the society. Once the traditional morality is defeated by the new morality, you'll see a new solidification of a "master morality" that will look different than the old one.