>how can we talk about separation >according to race when it >is clear that the concept >of race is a social >construction.
That is precisely why you would separate this society. Because some members of this society have created this idea of race and they hold it dear to their hearts, minds, wallets, and property.
It's not like we're talking about a good biological reason to separate, but rather a good social/political/economic reason.
Furthermore, this whole contention that race is a social construction and nothing more blinds the issue. The fact that race is a social construction and not a biological/genetic fact is inconsequential to people who are routinely and systematically shut out by this society because of their "race".