I'm ambivalent about this comment.
On the one hand, it's sensible.
On the other, well, the Democrat's own endless racism-by-correlation logic & rhetoric might suffice. So far nearly every flash mob theft I've seen like this over the years, dating back to the Apple store grabs, has involved almost exclusively black people. Blacks vote Democrat by a ratio of ~90%, don't they? I'm sure there's some remarkably stupid insight buried in this correlation that a Democrat would find sublime.
It would seem if it's kosher to call voter suppression that doesn't actually directly target people by skin color "racist" by correlation of those who it has practically effected, then it needs to be fair ball to look at these trends, and ask, "Why?" Sometimes there are matters of policy at stake. Sometimes there are matters of culture. I'm reminded of those who insist it's racist for merchants to more aggressively maintain vigilance against blacks, and yet when the rates of shoplifting per capita are presented confirming how much more likely merchants are to face "shrinkage" from blacks, this will be ignored by many who previously insisted the merchants were being racist.
However, before we get to the why, it's important to first establish an ethnic correlation to this phenomenon. This is anecdotal. Statistics would be interesting.