Why is it okay to be proud to be Black but not to be white?

I've often seen African women proudly celebrate their dark or chocolate-brown skin, and this is usually seen as positive and empowering.

I also frequently come across posts saying things like "I'm proud to be Black," which are generally accepted and often encouraged.

However, it seems that if someone were to post "I'm proud to be White," many people would react very differently, with some even considering the statement racist.

Why is there such a difference in how these expressions are perceived?