Why do people insult others racials?

some people who are not racist will insult others in a way that makes them sound racist. why?

if you do not like someone because they had a fight with you, why say 'i hate that black dog?' why not say 'i hate her?' saying someone is black/white/yellow/brown makes people think you are racist and do not have a reason to hate 'her' other then that.

do they think they look hard by doing this?

pleas post...