The word "mutant" implies otherness. It's not hard to label a person a mutant and disassociate him from humanity (think: Ned Ralston). Barring Morrison's somewhat ignored work on mutant culture, there's little flattering about the word.
Andrew Wheeler of ComicsAlliance points out how part of rejecting an unwanted label means means offering an alternative. Black people, for example, rejecting "negro" for "Afro-American". Now let's look at DC Comics: their empowered humans don't suffer the same stigma as mutants. Humans don't think metahumans are out to get them or vice versa. It's understandable; a "metahuman" is still considered human. Instead of mutant, why not metahuman?
If Havok had ended his speech with that question, we might be singing a different tune.