Occasionally people may have reasons for discrimination. For example, a woman might be the most suitable person for the job of counsellor at a women's refuge. The law permits this kind of sensible discrimination. Political correctness PC means using words or behaving in such a way as to avoid giving offence. It has been much criticised in recent years, but could be considered to be just good manners.
Some words are offensive and hurtful, and encourage prejudice and discrimination.
PC can become objectionable if it is a substitute for action to remedy a problem, or if it becomes an excuse for unfair discrimination. Human beings like to feel part of a group, and sometimes, in order to achieve this, put up barriers to protect the group identity and keep out outsiders. Human beings also tend to fear, or at least feel cautious towards, anything or anyone very new or different. This may be natural, but that doesn't mean it's good, or that human beings can't progress beyond these rather primitive emotions. Humanists promote happiness and fulfilment in this life because they believe it's the only one we have.