A few points

"we're all mixed to some extent"
Possibly so but I'm reffering specifically to BIracials. ie persons with two parents of distinctly different ethnic backgrounds. Be that Irish (white) and Thai (asian) or African American (black) and WASP (white). A person with two mixed parents doesn't come with the same issues or stigmas as a biracial person.

Furthermore having a few white ancestors in the past doesn't make you "mixed" in the biracial sense despite the emphasis some place on their pretty hair or eyes and how they're part this or that. Having one black ancestor that far back by the same reason does not make you black. How can a person seriously argue that because Mariah's father was biracial, she is black? She is at most 25% black. Meaning she 75% is NOT. How difficult is this to grasp? Wentworth Miller? FFS!!

"they identify with black so they're black"
So black is no more a colour/culture/heritage but a clubhouse open to membership simply because one wishes to join? I'm sure Eminem and Lady Sovriegn identify with black. So what? They're no more black than Derek Laud is white, not for lack of effort. As much as a biracial person feels drawn to one side you're seeing the playing out of parenting issues and not actuallity. It's denial mostly and it's a negative emotion. Usually people are driven to identify with black either because it's cool, all their friends are or more sinister like, they have been driven towards the only group who seemingly accept them on the surface by white people which brings me to...

"white people see us all as black anyway so effectively they're black"
It's not up to white people to define either mixed/biracial people nor black people. It's long past time we learned that.

They can't have it both ways/They have to pick sides
And most would prefer if they picked our side presumably. But that white side is always there in the unconscious of them and black people. It's an unspoken taboo which leads to them never really being on any side. Those who don't know theissues of colourism by now should catch up somewhere. Also in a sense this is defining mixed people by a standard we not they are setting. They must be what black people decide they must be or they're traitors... to whom? Realise they are 50% white in the first place and we won't be dissapointed by them nor compel them to be what they aren't or deny themselves. They stay being "black" and black people continue either uplifting them as the ideals of beauties in self destructive behaviour which breeds a superiority mindset in the mind of the mixed and a backlash of hatred against the mixed in a stupid cycle. Either a mixed person is unnecessarily glorified or unnecessarily hated to silly levels both resulting in unstable personalitys purely because of this picking sides business.

Latinos/South Africans
Not the same as BIracials. Understand that cape coloureds in SA and similar places elsewhere are not BIracial. They don't have two parents of distinct different backgrounds. Both parents and their grandparents to the nth level a few 100 years are all part of that mixed seperate group with it's own community/culture history distinct from both blacks and whites. In terms of the social issues that come with BIracials mixed people are not the same. As a group they aren't identified the same simply because mixed people in these communities don't have that picking sides business or torn feeling in their heads. However politically/Socially and idealogically they are the same in one way....

Those against the idea of a seperate racial category are really against what is best and most stable for mixed persons themselves and where evidence shows they are most stable. Not torn between two worlds hopping like aliens, not lying to themselves and declaring they're one thing soley but being exactly what they are. Biracials should be part of the seperate racial classification. Many of them have openly expressed that they want this. Yet when some here see their websites we get upset with them for stating this. Why? It's so much better for Africans too. Not in the sense that our fragile egos can't take mixed people around confusing us but that it's adopting not only a white standard of what black is but their whole purity reasoning along with it.

Mixed people are simply that. What it says on the tin.