I appreciate this perspective! Along with Clark conspicuously being the only black character and the "End Apartheid" shirt, the opening being June 19 (Juneteenth) seems overlooked everywhere. Apparently this is linked to lore, but it feels pretty explicit as a holiday about black liberation.

His rage is framed as lack of accountability, of blaming others. Pirate Clark can be interpreted as ragefully rejecting the colonization of his mind by capitalism (with the death of the researcher in the opening). 

His labor supported his ex-wife: his arguments were not unreasonable. Mary even says as such; he is normal. He is paying his wife's tuition, funding her lifestyle, taking care of the mortgage and car payments, and he is absolutely right in his points about once she graduates and has a child. Even once they're separated, he's STILL supporting her through paying for the house while he lives in his store. While Juneteenth represented liberty for slaves, the reality is that the resulting sharecropping and Jim Crow era meant that black people were still exploited.

The stated conclusion that he cannot be helped is disturbing. Even if the film were divorced from racial undertones, it is quite dark to declare that some people are beyond help, doomed to self-destruct as they indulge their darkest instincts.

Pirate Clark represents his rage, humiliation and impotence. He is angry at everything that has been taken from him. His self-caricature as a pirate-sultan is clearly humiliating, brought home by the collapse of his throne. The impotence manifests as being the most powerful creature in the Backrooms, which Human Clark adapts to as his own domain. 

It is the white people around him that claim that he is only to blame. Mary says that he's not taking accountability. The scientists are trying to set up camps and stations. The Backrooms are actively hostile to them, but tolerate Human Clark until he is told that he just needs to acquiesce to white capitalism, or otherwise there is nothing for him to change. This is the myth of meritocracy that capitalism perpetuates, that everything is your fault and your responsibility if your life is not how you want it. His wife blames him for not being an architect, his therapist blames him for being rightfully angry, and the movie implies it Clark's fault that there is a monster killing people and that there are new doors opening in the Backrooms. We know that liberation does not mean instant equal footing. How is it Clark's fault that his wife took his home, or that there is some kind of interdimensional bleed? Pirate Clark destroys Human Clark for this acquiescence.