There is truth to this.
I've noticed that mixed Blacks always have this aura superiority about them. Especially, those of high yella or red-bone complexion, and especially females. I think it's the mixed blood that taints their minds.
Also, A mixed person isn't going to have the ideal traits suited for an African environment. He or she won't have the proper skin tone, perhaps they won't have the proper physique, and they may not have the proper digestive traits or immunities to survive the Sub-Saharan African environment while a pure African would have no problem. Africans are under constant selective pressure, and infusing blood that hasn't been selected for may not be the best idea.
We must recognize that human beings are biological machines, fine-tuned, by evolution. We try to socialize-out our revulsion at the interaction with other races, and we call such instincts primitive and of a less civilized time. However, mother nature has ingrained us with group-think and tribalism for a reason, and from the fossil record this behavior seems to be a very ancient adaptation. Fooling with what mother nature deemed to be effective and efficient is going to be bad for us in the long-term.