It is actually pretty obvious, if you pay attention.
The fertility rate in the US of US citizens has dropped well below replacement rate. All of our population growth comes from immigration, legal or otherwise, and their fertility rate is much higher than that of US citizens. Hence “...somebody else’s babies.”
The fertility rate of Muslims everywhere is notoriously prodigious. Anyone who denies it is both a liar and an idiot. Further, they’re not interested in integration but colonization.
Someone needs to prove that King said anything wrong
If immigrants are citizens, then they are not “somebody else’s babies”.