The relevant issue is not whether xenophobia is biological (of course it is biological). The issue is whether a dominant group (whites) having a specific xenophobic reaction to an oppressed group (blacks) is possible to prevent (and again, of course it is preventable).

I am not xenophobic of my cat, because though it is different it is no longer unfamiliar. It's like you are asking my cat to become more human so that I am no longer afraid of it, when really it is I who must become more familiar with my cat so I can stop being afraid.