Because the "white race", unlike the brown or black folks, has done a lot of bad things
Like wipe out several civilizations in North and Central America. Say 30 million folks.
Once that was done, the whites (with a little help from some Arabs), kidnapped a few million black folks and used them as slaves.
You might also recall the colonial period, where white folks went out to every corner or Africa, Asia, and Oceania and subjugated and killed millions of brown and black folks, and took over their countries.
Then you may recall WW2, where the white folks got sooo ornery, they started killing each other, to the tune of about 30-60 million of them, depending how you count.
Then there's the few 100 thousand the white folks fried at Hiroshima and Nagasaki. And more thatn that which dies slow painful deaths by radiation afterwards.
Just recently, we USA white folks killed at least 140,000 Iraquis for no discernible reason, and with no remorse, guilt, or apology.
So you see the whole concept of "White pride" is a bit tarnished. Yes, whites are good at working hard and innovating. Also reasonably charitable. But any sense of pride has to be tempered with a very large dollop of shame for our behavior toward others.
