Assigning words relative levels of offensiveness is irrelevant to the issue here...that being racism. There is an entire spectrum of offensive racial terms spanning all races and regions. Trying to rank them according to whatever their perceived "offensiveness level" happens to be is a waste of time.
The actual problem is the underlying racism that leads to their being used at all. Racism is racism. There is no legitimate stratification of it, and so stratifying the racist words people use seems even less meaningful and arbitrary.
If we're going to go heavy against one word relative to another, especially if it is done along specific racial lines, then we're right back where we started with the same offensive and counterproductive double (or triple, or whatever) standards that entrench and ossify racism, rather than actually oppose it.