This episode should serve to teach you not to take a humor show too seriously. Comedy Central doesn't have a sacred contract to give you what you want to see. Stop whining about this "horrible injustice" and relax. Your life doesn't depend on finding out who Cartman's father is.
Didn't Stone and Parker say that they wanted the show to get weirder and weirder until people are scratching their heads? Stagnation and repetitiveness would be the death of the show. I'm glad to see that they are not afraid to be experimental and creative.
Remember: They don't owe you anything, crybabies. Just relax and enjoy it.