I'm hesitant to draw conclusions, even temporary ones, without adequate evidence, and I do not see adequate evidence here. That does not mean that I deny the possibility of some ethnic groups being particularly susceptible.
As for AIDS, I remember the early days of it spreading, when it was thought that Haitians were particularly susceptible. It turned out that the large number of Haitian cases were the result of American homosexual tourists using young Haitians as butt boys.
Until we have adequate data to analyze, guesses are just guesses, not informed ones.
Caucasians are resistant to HIV - via the CCR5-delta 32 allele. Persons who are homozygous for the CCR5-delta 32 allele are completely resistant to HIV, while those who are heterozygous are relatively resistant and slow to come down with full-blown AIDS. Approximately 16-35% of Caucasians are heterozygous for CCR5-delta 32, and 1-4% are homozygous, while almost no Africans or Asians carry this gene.
Having resistant individuals in the chain of transmission stops transmission on a greater than 1 to 1 ratio. If you aren't infected then you won't infect anybody else, and the people you didn't infect are not going to infect others.