"Earth is flat" is a objective statement. "I experience consciousness" is subjective, similarly to "I am experiencing pain". If someone tells me "pain doesn't exist" while I know it exists, because I have experienced it, I can be certain that that person is wrong. Even though I can't prove it to him.
"Earth is flat" is also a subjective experience argument. Yet mostly nobody takes it seriously anymore. I hope "qualia" will be like this soon too.