> At low to moderate levels of B, an increase in B should have a negative influence on housing value if Blacks are regarded as undesirable neighbors by Whites.

Isn't that true? It's almost a tautology.

(Bad things can be true.)

It's significantly more complicated. This presumption assumes that black people are responsible for depressing housing values and ignores a myriad of other factors (i.e., it assumes that this is caused by black people moving in, not white people moving out). It's such a narrow view of the problem that it makes me question the motivations of collating such data to begin with.

For example ignores the fact that on the whole black people are significantly poorer.

In Boston the average white family has a net worth of $200k+ while black families in the same city have a net worth of <$10 (that's not a typo, it's less than ten dollars). Poorer people by nature can not afford houses in more expensive neighborhoods, so naturally you have a concentration of black people in poorer neighborhoods... it's not because white people find black neighbors undesirable, it's that black people are disproportionately poorer.

This kind of oversimplification tends to perpetuate a lot of negative stereotypes about black people while hand-waiving away the chronic issues black people are faced with that creates this kind of disparity.

Isn't that saying that lower house prices are caused by racism?

In an incredible whitewashed way that's very familiar to anyone that lived during the Jim Crow era, yes. Note that it doesn't say that white people leave because they're intolerant of black neighbors, but paints black neighbors as undesirable.

Either way, it's a dramatic oversimplification. Black people are also significantly poorer than white people, so it's also likely that black people can only afford to move into a neighborhood as property values decrease... yet the people who collated this data chose to make a different assumption.