Your concerns are largely unsubstantiated.

Even if you're somewhat ethnocentric, the projection of US racial fertility trends by Edmonston et al for 2100 doesn't seem worrying:

38.8% white 
30.6% Hispanic 
15.6% black 
14.9% Asian and Pacific Islander
1% American Indian

Out of all 550 million US citizens, the absolute number of white people will be only a few million less than today, 209 million.

If you're more concerned about the nation-wide effects of decline in average IQ and dysgenics: Richard Lynn estimates that US lose 0.9 IQ points per generation. By 2100, Americans will have lost on average 4 IQ points. Improved healthcare and mind-enhancing technologies should easily compensate for this loss, and by this time we'll be probably either cyborgs or dead.
 
I understand that imageboards should be permissive to edgy content, but "targeting individuals because they belong to specific ethnic groups" is the literal definition of "racism" and has a very poor historical record in making societies better. It also puts other important submissions (black pill, dramas in the rationalist community) in a bad light.