There really isn't a clear demarcation between a lot of Ukrainians and Russians. Up until 20 years ago, they were the same country, essentially different state, with Russians moving there like someone in the United States might move to Texas. One day you wake up (in 1991) and Bam! you are now Ukrainian. It will take generations to sort out.
Yes, I know it's complex, though I'm not sure the Texas/US analogy is quite right (it may be taking the correct idea a little too far). Part of what nationalism does is strengthen boundaries that were previously quite squishy, so Joel has no doubt had to deal with some of these issues.