I think there's an oversimplification here, that seeing someone's race is going to determine your reaction. You see lots of things in that same second. You see their clothes, their posture, gait, and other body language. In fact, those other things may be easier to determine than skin tone is, particularly at night. Clothes and body language may correlate with race or ethnicity, but there's no direct causal relationship.

You mention race because it's a lot easier to categorize based on race than based on a hundred different clothing and body language parameters, but it's those complex non-racial, non-ethnic things that really make your decision for you about whether someone is likely to be a threat.

Many more blacks or hispanics, on the street in an inner city or bad neighborhood, may exhibit nerve-inducing fashion sense or body language, but you're still not nervous about their race, you're nervous about those other things, and the location (alley? possibly late at night?), and forming a post-hoc explanation based on race because it's cognitively simpler.