Interbreeding with other races is different than associating with other races. Working with them is fine, even socializing, yet I believe in keeping some of each race pure. Each race will physically and psychologically strong/weak environments, the biological variation. In general the within group variation masks the between group variation, but many studies have teased out some differences. Those provide some advantages to specific breeds for some things, but cultural, religious, educational and experience are much bigger factors. Breed provides the genetic material, nurture provides much more conditioning for life.
The selection of a mate to reproduce with is critical for the next generation. Those in power, the rich recognize and tend to stick together, a money criteria in mate selection. This likely purifies some characteristics, like stuck-upness, whatever the pc term is. Like tend to stick together, but when the privileged few are in control, privilege will remain. For this reason, money should be taken out of politics, so that the voice of the people is the voice of the people, not the voice of the wealthy, as it is in the US today, and less so in Canada.