Racism - a step too far sign now

Racism... Why does the word instill fear among everyone, isn't a human right to have freedom of expression? Then why isn't a person of any race allowed to label another by their race, like calling someone a 'paki' when they are actually Pakistani, which incidentally is meant to mean pure when translated from Pakistani. Another problem with racism is positive discrimination, where a person can claim that they have been unfairly treated just because they are from an ethnic minority and a when person from an ethnic majority has been racially abused then why do the culprits receive no punishment at all.