when we're so positive (as we should be) about people born with male bits who "self-identify as women".
So do these males suffer periods, anxiety about biological clock vs first child, worrying about pregnancy (wanting it or not wanting it), have sex as a woman with a man without telling him that born as man, be anxious about sterility ...
Certainly there are some similarities, but a white person wanting to identify as black isn't on the same level of complexity as transgender issues. Some people are born with ambiguous sex and some have been surgically assigned as women at birth and later have huge issues.
Also there is a huge spectrum of personality and emotion such that people really believe they are the opposite gender to what their physical body portrays. There is a huge spectrum of transgender issues. People born with male bits who "self-identify as women" is one aspect and being "positive" isn't any solution to their problems. As early as 1930s womb transplant was tried for such a man.
Race really is artificial. Someone who isn't an African-American pretending to be one doesn't help remove racism. Gender unlike Race, is real and Genetic. The solution to Gender issues of equality isn't to pretend Gender is a social construct. People who internally are convinced they are the other Gender to their body do not want to erase Gender. They want to be the other Gender. They certainly need understanding and support and IN NO WAY should be likened to a person "identifying" with another race or vice versa.
A white person claiming they identify with "black" re-inforces racism. There is no genetic basis for Race or Racism.
Race unlike Gender doesn't exist.
Race is a social construct
https://en.wikipedia.org/wiki/Race_(human_classification)
Gender has gathered social baggage, but it's real. Modern society is trying to redefine gender independently to sex or abolish it. This can only lead to increased confusion, frustration and unhappiness. If Gender was as imaginary and purely a social construct, then by definition "transgender" people wouldn't exist. They exist because unlike race, gender is real, sex dimorphism is real too.
A lot of confusion around Gender:
https://en.wikipedia.org/w/index.php?title=Sex_and_gender_distinction