I agree that the individual comes first and that there is nothing wrong with a boy that likes caligraphic writing. Everyone should be able to do what they like without outside forces telling them how they have to be like.
But I think that there are inherent differences between the sexes (talking about averages not individuals!). And these are not just social constructs but rooted in our biology. From the perspective of evolution that makes a lot of sense. When evolution was able to construct mechanisms as complex as our eyes, it certainly figured out that in an asymmetric reproduction mechanism symmetric sexes is not the optimum.
But as I write above this is not really that meaningful. All individuals have the same rights, independant from their character or abilities. Before it was wrong to expect people to conform to their 'gender roles', now it is wrong to create a new unisex gender role for everyone. Becasue both is forcing people of their own path.