‘Cracker’ got into regular use in the 70’s and 80’s in reference to white crackers (the kind you eat with soup) NOT anything so dramatic as the “cracker” of a whip.
It was a demeaning way to refer to a white person, like calling them white bread.
Yes, it is as bad as ‘the n-word’ but not as bad as the OTHER ‘c-word’
Use of cracker as derogatory is around 200 years old. Used in Scotland for braggart (an annoying noise), and in the US as short for corncracker (poor white farmer).