Why is Barack Obama called black?

Seriously, I have no idea why people call Obama black.

He is HALF BLACK AND HALF WHITE, DAMMIT. Half/half doesn't qualify a person one way or another; you don't call a person who is half boy and half girl a boy or a girl, (s)he's a hermaphrodite. Same applies for race.

Now. let's think why they keep calling him black. Let me give an example: say an Indian-Chinese mixed blood became the president of India. Everyone would go "Wow a Chinese became the president of India!!!". On the other hand, if the same dude became the president of China, everyone would say "Wow an Indian became the president of China!!!"

From this we can derive what I call Billy's first law of sociophysics:

"A mixed blood person in a society is always identified with the minority race in his/her composition."

Now, you may say to me there are exceptions. Mahathir, who was once our prime minister, was half Indian but people don't think of him as Indian. Right?

True, but there are several factors that make him the exception.

One. He looks Malay.
Two. He has a Malay-sounding name and identifies himself with the Malay culture. If he called himself Muthu Arisamy or something like that I bet he wouldn't make it to the Prime Minister post.
Three. Other politicians at the time still took potshots at him because of his Indian heritage.

So although Mahathir has bent my first law a tad bit, I think it still holds in general.