Why are mutants not classed as humans ?

I would usually assume it would be like a prejudice saying other humans would just say to dehumanise mutants, buts its something even mutants reiterate. But to me it just doesn't make sense, why they wouldn't be classed as humans? Genetically there would be very little difference between a human and a mutant. Humans and mutants can also have children with one another and some mutants can have human children while some humans have mutant children. When a whole new species is introduced it dosent happen like that. Plus mutants experience the same emotions and have the same needs as any human. And as the x men are supposed to be like a representation of discrimination between people surly it would be more logical to say they are human as well but just with powers and evolving or something.

Edit : i understand its also possibly a representation of dehumanising a group of people . But in the comics and shows like x men 97 mutants class themselves as seperate from humans which is what confuses me.