Why is graffiti racist?

Graffiti in and of itself is not racist-- there has been graffiti for centuries, in a number of countries. Of course, graffiti is considered vandalism in some cases, since it defaces public property. But not all graffiti carries racist sentiments: some graffiti is just kids signing their names, or politically-motivated adults writing a slogan. There is a stereotype that graffiti comes from gangs (African-American or Hispanic gangs especially), but this is a generality. Often, kids who write on walls are just trying to get attention and are not in a gang at all. But yes, it is true that in some places, some of the slogans written have been racist, and this was especially true during the fight for civil rights, when opponents used graffiti to voice their displeasure. However, it should be noted that a lot of graffiti these days tend to be either anti-Semitic or anti-immigrant.