Because the parent comment stated "Yes, the basis for the hypothesis is fried chicken -> black people and craft coffee -> white hipsters" as if it were a matter

Because the parent comment stated "Yes, the basis for the hypothesis is fried chicken -> black people and craft coffee -> white hipsters" as if it were a matter of fact. The blog post makes no mention of skin colour at all (that I can see) and the racial connotations are entirely those of the parent - hence injecting racial bias.