Nothing about the concept of carrying capacity is inherently fascist. Carrying capacity is just putting a number on the concept of "infinite growth cannot occur in a finite system." If an ecologist is trying to calculate the number of horses that can live on an island long-term, for instance, nothing about that project is fascist.

At least on this matter, the fascism crops up in the proposed solutions. "We should cull people in the global south and keep the remainder in perpetual poverty" is a fascist solution. "We should improve the material conditions of the global south and guarantee women economic and political rights" is a socialist one.