Clearly this discussion can, and indeed must, continue  endlessly. 
This is the conclusion of a neuro-scientific study into responses according to race which may be more scientific than the IRR study: 
"The studies are numerous and conclusive – we have a significant race problem in empathy. While it will be hard for most of us to know whether or not our brains are reacting equitably in situations that call for empathy, it should be easier to build concern and care for people of other races on a conscious level. "
Or, how about this bit:
"the most damaging part of the racial empathy gap – we bury it deep in the subconscious in layers of denial to protect our social reputation. We might explicitly deny our internal reactions, but implicitly we follow their whispered mandates right down the line. "
https://aeon.co/essays/unconscious-racism-is-pervasive-starts-early-and-can-be-deadly