Yes, "cracker" is a derogatory racial slur. It comes from "whip-cracker", ie, a slave driver (this was actually news to me, since I thought it referred to the pasty whiteness of something like a Saltine cracker). As for being comparable to other slurs like "raghead", "******", "kike", or "*****"...well, I can only speak for myself, but I'd have a hard time being offended if someone started calling me "cracker" as though it was supposed to be an insult.
Now, there are other slurs for white people that I think are much more offensive. "Trailer trash" comes readily to mind. I've also heard "Upper-middle class" used aggressively as a slur for white people (the same way one might refer to poor black people as "Inner-city youths"), which I think is a little bit worse because it mixes classism with racism (assuming black people are poorer than white people, and from that assumption painting a picture that white people are "the rich" who are oppressing "the poor").
Of course it is possible to be racist towards white people. White people are a race. If you make a judgment of a member of that race on account of his or her being a member of that race then you are being racist. That's what "racist" means.
Now, there are other slurs for white people that I think are much more offensive. "Trailer trash" comes readily to mind. I've also heard "Upper-middle class" used aggressively as a slur for white people (the same way one might refer to poor black people as "Inner-city youths"), which I think is a little bit worse because it mixes classism with racism (assuming black people are poorer than white people, and from that assumption painting a picture that white people are "the rich" who are oppressing "the poor").
Of course it is possible to be racist towards white people. White people are a race. If you make a judgment of a member of that race on account of his or her being a member of that race then you are being racist. That's what "racist" means.