Treating race as a fiction is just as irresponsible as believing there are more than two sexes.
Then you should tell me, who do you believe is responsible for providing race and gender identities?
No one should care about these two categories and they are only in one's mind that is why it doesn't exist.
If an enormous population has been sharing the same sentiment before these genders terms even existed proves it's all valid. Your words of invalidating all these groups is essentially erasing who these people are. It's best to read up on why they feel this way, and why they need to assign more labels.