I'm not missing the point; I've already said, I disagree.
First of all, the mugger in this discussion is not simply "attacking" people for their wallets. We have specifically stated earlier in the thread that, in our hypothetical situation, the mugger "killed" the person he robbed. That automatically elevates the crime from robbery to intentional murder.
Second of all, a mugger who is "killing" people and taking their wallets is not more likely to be rehabilitated than a person who is killing people based on personal biases. I highly doubt that a mugger is going to rob a few people (and kill them, mind you) and then think "Gee, I have enough money to last me a while, I think I'll get a job now." Someone who actually thinks like that wouldn't kill someone in the first place. Furthermore, if we agree that this murderer/thief does deserve a chance at rehabilitation, I feel that a racist killer does as well.
Finally, we're arguing over those who murder someone should be punished differently, purely because of the reason they committed the crime. If a person kills someone due to racist beliefs, it is no worse than killing someone because he or she wanted their money; the motive is different, but the crime is still premeditated and intentional. In my opinion, it's stupid to differentiate when dealing out punishment.
I agree that motive is paramount in determining guilt, but not in assigning the degree of discipline.