People who do not conform to their gender roles are not a different gender

The argument

Some women are masculine and some men are feminine. That doesn’t mean that they are some different third gender. Just because someone does not conform to their gender roles does not mean that they are a different gender. There are plenty of “tomboys” and feminine men who are perfectly happy being the gender that they were assigned at birth. Women can feel manly and not be men, and men can feel girly and not be girls. People who identify as nonbinary are really just rejecting the gender roles of their assigned gender. This rejection of gender role does not equal a rejection of one’s assigned gender.

Premises

Counter-arguments

The existence of feminine men and masculine women does not negate the existence of nonbinary people. Nonbinary people do not just feel "girly" or "manly"; they feel that they are not men or women. Feeling like you are not exclusively a man or a woman is an entirely different phenomenon than feeling like you're a girl who doesn't want to be girly or feeling like you're a man who has some feminine qualities. Not identifying with your gender is completely different than not identifying with your gender roles. Tons of women and men reject their traditional gender roles but still identify as women and men respectively, but they are not the same people who claim to be nonbinary. A nonbinary person will generally feel uncomfortable being addressed as a man or a woman, while a masculine woman or a feminine man will not. The two phenomena are completely separate, and the existence of one does not negate the existence of the other.

Rejecting the premises

[Rejecting P1] True, and it establishes nothing about a different group. That some people are content with the sex they were assigned while departing from its social expectations shows that role and identity can come apart — which is the distinction the argument goes on to collapse, not one it can use. [Rejecting P2] The premise substitutes its own account for what the people described actually report. Nonbinary people generally describe not being a man or a woman; a masculine woman is content to be addressed as a woman, while the discomfort reported in the other case is with the address itself. These are different reports about different things, and the argument reclassifies one as the other without evidence. [Rejecting P3] The step restates the conclusion rather than supporting it, and it proves too much: on the same reasoning any first-person report could be overridden by an outsider's account of what the person "really" means — a principle the argument would not accept applied to its own side. The classification question is separately addressed by the historical and anthropological record of societies that have recognised more than two social categories.