discrimination
When someone treats the other with different races, species, nationality, genders, ages, religions, social background, occupation, ideology or sexual orientation with bias and disrespect.
Note that this tag emcompass the general discrimination, for specific discrimination against races or ethnicities, see racism, for discrimination based on sexual orientation, see homophobia, for discrimination based on disabilities, see ableism, for discrimination based on transsexuality, see transphobia.