1) SJW isn't a bad thing, like racism. social justice (the literal term) is what all people want in their society. It's preached by nearly every religion (the idea that the poor are equal to the rich, the black people equal to the white, etc).

2) Racist is an adjective but SJW is a group affiliation often attributed to people who don't wish to be affiliated that way. A person can say a racist thing, but no one can do an SJW thing. We can qualify certain things and statements as racist or not. We cannot do the same with SJW. SJW will always be used to denigrate someone. Racist, however, can be used analytically and without malice.

wrt point #1, SJW and Social-Justice Advocate are different terms. Justice is a subjective term, the word itself may have a positive implication, but the implication of "SJW" is that their brand of social justice is neither just nor good.

I disagree with point #2 though: the word "racist" is used to denigrate (label people who do not accept the label) more than otherwise. A person can absolutely say an "SJW thing" - the kind of thing an SJW would say. This may be ambiguous, but so is racist; it depends on a personal definition of what constitutes racism just as mush as SJW does.

In fact, willfully creeping the scope of words such as "racist" to include e.g. microaggressions is partly what differentiates SJWs.