Black lives matter.

So white, pink, yellow and grey ones don't?

I assume that the "too" has been dropped to maintain a catchy feel. Black lives matter too. The "too" is assumed, presumably. An alternative would be "all lives matter".

When a campaign title like this is created, people choose something catchy, concise and short as possible. "The lives of black people matter as much as all others", is too long winded. Hence we get black lives matter, which has a hidden, unintended, alternative way of reading it. Black lives matter the most, black lives are important the rest maybe less so.

The real point of this piece is that when you campaign for one group you shun another. The lives of the disabled, the yellow, the meek get pushed further down the agenda.

Does a half cast person get white privilege and sympathy for any black related racism?

How about using this tool to see when you are "black" enough to count in the black lives matter campaign. Note that it is shades of brown/pink, as I have trouble finding actual black coloured people in the world around me.