This has been discussed before and if I remember right there was also a line of thought that it was more a cultural phenomenon than particularly racial. After all there is a wide racial range among Latins and a wide -none tolerance among Asians.
Cultures with larger more tightly knit families were thought more tolerant of -none than those with smaller more nuclear families. Lots of brothers, cousins, and uncles in close proximity leads to more comfort around men generally. Whether they are comfortable in a sexual situation would still depend on individual experience.
Great thread by a great poster!