I don't think what they mean is that when a minority goes to SO and they get a condescending response it's because of their race/ethnicity/gender.
What they mean is that, since minorities might have insecurities about their ability to code because there are not that many people who look like them in the industry, when they receive a condescending response their insecurities aggravate. Therefore, SO can be consider more hostile for minorities.
What they mean is that, since minorities might have insecurities about their ability to code because there are not that many people who look like them in the industry, when they receive a condescending response their insecurities aggravate. Therefore, SO can be consider more hostile for minorities.