If it's not the imgur album ReadFanon linked maybe you're thinking of a comment in a Hexbear post that linked to that album?

Let us consider the question of ass versus tits.

Which is the superior set of flesh mounds? First, consider this. Titties are not universal to all. Tit size is dependent upon genetics. Simply put, to prioritize the tit would be to promote the genetic ability of a person. It would be fascist propaganda! The working class should not depend on genetics for sexual salvation. In addition, the only way to change titty size is by expensive cosmetic surgery. Therefore, the only way to subvert boob genetics is to have money, to have capital. The promotion of boob idolization only allows those with money to attain the top level of boobiness. Much like wealth is concentrated among the capitalist pigs, boob attractiveness is concentrated among the monied classes. There is no recourse for the working class to attain the top level of tit appreciation, no sexual mobility. The system has been rigged against them, and the working class must tear down the bourgeois titty state in order to build a sexual world where everyone has value. If the Great Proletarian Sexual Revolution is to take place, then I propose that we must not seek to replicate titty liberalism. Continued fetishization of the tits will only result in will only lead to the same result. Titties can only be objectively attractive for so long before they sag, so the contradictions of mammary society will bring those with unsavory breasts to the bottom of society, while those with good tits at birth or at least those with redistributed titties will rise to prominence on the backs of the global titless class. It is social mammocracy at best, and by that definition, is liberalism.

Instead, let us consider the ass. The ass is the true sexual organ of the working class. All asses are valued. Be they black, white, Asian, Indigineous, male, female, nonbinary, old, or young, all asses have value. Every ass, no matter the gender, age, or color, can be rimmed, sucked, fucked, stretched, or whatever. Pleasure of the ass is available to all members of the working class, while pleasure of the tits is only available to the genetically blessed and moneyed. There is no need for one to win the genetic lottery to have a good ass. Ass is the true form of socialism: all is for all. Everyone can have an ass. In addition, improvement of the ass is not limited by money. It can be toned by physical exercise. Like a better world, a better ass is obtainable by all of the working class. The bourgeois state cannot deny access to a better ass via healthcare costs, because a better ass is only for the worker to seize. The ass is the organ upon which the worker takes their due rest, it is their respite from the cruel capitalist world. The ass is like the worker, it is soft and it has potential to be great. It can be valued as it is simply due to its universality, or it can be hardened like the revolutionary working class, formed into the buns of steel that will strike down the bourgeoisie and bring about socialism. Like the working class, ass is eternal, and it is the working class alone that ensures that the dictatorship of the gluteus proletariat remains toned, ready to sit on reactionaries and provide the foundation of a world where the worker is on top.

Down with the bourgeois titty state! Long live the Working Ass!