Empathy can switch quickly after team re-assignment.
In 2013, Van Bavel told me of a trick that sounded so simple and hopeful. Sometimes he’ll switch a red-team participant to the blue team and vice versa. “We say, ‘Listen, there’s been a mistake, you’re actually on the other team,’ ” he told me then. “And the moment we do, we completely reverse their empathy. Suddenly they care about everybody who is in their new in-group.”
That might be simple in the lab, but in the real world, these feelings are more deeply entrenched. But even in the real world, experimenters are showing there are ways to reduce bias. (Source)
Empathy is almost always bounded by group identification. See Group-Boundedness of Empathy